Aerospace

Authors: Tabitha Grace Keyes, Sascha Klöker, Sören Reinhold
Last updated: October 2nd 2023

1 Definition and Relevance

This Wiki article is about the aerospace industry. With this article, we want to focus on sustainability in the sector by first looking at the industry’s general impact on sustainability and the environment and how it can be measured. This is followed by the sustainable strategies and measures. Finally, we will take a look at the drivers and barriers of sustainability in the aerospace industry. Before we dive too deep into the topic, we will first explain why the sector is relevant and give some basic definitions.

There is no comprehensive definition of the aerospace industry in the literature. According to the United Nations’ International Standard Industrial Classification (ISIC) Revision 3.1, the aerospace industry belongs to Class 3530 ¹ United Nations. International Standard Industrial Classification of All Economic Activities ISIC Rev. 3.1. (2002). , which includes the manufacture of aircraft and spacecraft of non-space items such as passenger and military airplanes, helicopters, and space items including spacecraft, satellites, and shuttles.² OECD. “Overview of the aerospace sector: background”, in The Space Economy at a Glance 2007 OECD Publishing, Paris. (2002). Examples of manufacturers in the aerospace industry are the two largest commercial aircraft manufacturers Airbus and Boeing.³ He, S., Hipel, K.W. & Kilgour, M. Analyzing market competition between Airbus and Boeing using a duo hierarchical graph model for conflict resolution. Journal of Systems Science and Systems Engineering, Volume 26, pages 683-710 (2017). The two manufacturers have built and delivered a combined 1140 aircraft in 2022 alone and still had a combined 712 open orders. ⁴ Jones, M. Boeing vs. Airbus: The Key Reason Why Airbus Stock is Better https://www.nasdaq.com/articles/boeing-vs.-airbus:-the-key-reason-why-airbus-stock-is-better (2023). Boeing had annual sales of $70.54 billion that year, and Airbus had annual sales of $64.06 billion.⁵ Statista. Umsatz der weltweit führenden Flugzeughersteller und Zulieferer im Jahr 2022(in Milliarden US-Dollar) https://de.statista.com/statistik/daten/studie/30808/umfrage/umsatz-der-weltweit-fuehrenden-flugzeughersteller/#:~:text=Airbus%20und%20Boeing%20sind%20die,vorn%2C%20was%20die%20Flugzeugauslieferungen%20anbelangt. (2023). And those are just the numbers for the two largest commercial manufacturers in the industry. To give a comprehensive financial picture of the manufacturer’s side of the aerospace industry one would have to include other manufacturers like Lockheed Martin or Raytheon Technologies as well as all major suppliers. This would go beyond the scope of this wiki. However, the figures do show that the manufacturers are large employers on the one hand and have a lot of financial capital at their disposal on the other.

The aerospace industry is not only about manufacturers but also about the complete air transport of passengers and goods as well as all the necessary services to be able to provide this. In the literature, the term aviation is often used for this. The term “aviation” includes both civil air traffic offered by the airlines and the transport of cargo with commercial aircraft, as well as military aircraft.⁶ Encyclopedia Britannica. Aviation https://www.britannica.com/technology/aviation (2023) Aviation plays an important role in the transport sector to bridge long distances in a relatively short time, be it in the context of consumer business travel or the field of tourism.

The aviation sector alone employs about 87.7 million people. Of these, about half are employed in the tourism sector (44.8 million), and 11.3 million are directly employed in industry, i.e. the employees of airlines, airports, or air traffic control operators. The remaining jobs are in jobs along the supply chains. These employees contributed §3.5 trillion to global gross domestic product (GDP) in 2018 alone. For comparison, if the sector were a country, aviation would be the 17th largest country in terms of GDP.⁷ Airbus. Non-Financial Information Annual Report (2021).

In summary, the aerospace industry is a large, broad, and diverse industry that covers everything from the manufacture of individual components and entire aircraft to the transportation of passengers and goods by air, to all the services that surround it, such as the operation of the airport. In addition, there is the military aviation sector as well as government and civil space programs, like from NASA or SpaceX.

2 Sustainability Impact and Measurement

Due to its many facets, aerospace also has various influencing factors that affect sustainability. In the individual sub-sectors, different factors are more critical and more relevant than in comparison to other sectors. In the following, the individual factors are discussed in detail, taking into account relevant literature and data. In addition, the extent to which the individual impacts can be measured will be discussed. Based on the results, the impact on the sustainability of aerospace will be compared with other industries and sectors.

2.1  Impacts of the aerospace industry on sustainability

The aerospace industry is an ever-growing sector that consumes a lot of energy in everything from manufacturing to operating an airport to flying an aircraft. At the same time, it is the largest consumer of fuel in the transport sector.⁸ Dias, V.M.R., Jugend, D., de Camargo Fiorini, P., do Amaral Razziono, C. Antonio Paula Pinhero, M. Possibilities for applying the circular economy in the aerospace industry: Practices, opportunities and challenges. Journal of Air Transport Management, Volume 102, 102227 (2022). The large consumption of energy alone poses great challenges in terms of sustainability. These challenges are made even greater for the industry by the fact that aerospace is still dependent on fossil fuels. Currently, the most widely used fuel by airlines is aviation jet fuel, and this has one of the most critical negative impacts on the environment of the whole industry.⁹ Franchino, M. Framework for Sustainability in Aerospace: A Proof of Concept on Decision Making and Scenario Comparison. In: Kohl, H., Seliger, G., Dietrich, F. (eds) Manufacturing Driving Circular Economy. GCSM 2022. Lecture Notes in Mechanical Engineering. Springer, Cham. (2023). The use of aviation fuel based on paraffin leads to emissions that have a negative impact on climate change and contribute to global warming. One of the reasons for this is the CO2 and greenhouse gas emissions produced by the use of carbon fuels.¹⁰ Abbasi, T., & Abbasi, S. A. Decarbonization of fossil fuels as a strategy to control global warming. Renewable and Sustainable Energy Reviews, 15(4), 1828. (2011). These greenhouse gases trap the sun’s heat in the earth’s atmosphere, causing the earth’s temperature to rise. This also results in extreme weather events, such as rising sea levels.¹¹ O. Yoro, K. & o. Dadmola, M. CO2 emission sources, greenhouse gases, and the global warming effect. Advances in Carbon Capture Methods, Technologies and Applications. pp. 3-28. (2020). Furthermore, aircraft emissions contribute to the formation of smog. Smog forms when pollutants from emissions react with sunlight and heat in the atmosphere. Smog can lead to various health problems such as respiratory illnesses and cardiovascular disease.¹² Mishra, S. Is smog innocuous? Air pollution and cardiovascular disease. Indian Heart Journal, Volume 69, Issue 4, pp. 425-429. (2017).

This leads to the fact that the choice of fuel has a massive impact on sustainability in the aerospace industry. Not only are the airlines and aircraft manufacturers relevant, but also the airports themselves. The definition of environmental sustainability in the context of airports is disputed in the literature. Some define it in terms of different categories of environmental impact. At the same time, others limit the definition of environmental impact in the same way as the traditional impacts of aviation, such as emissions and noise. Ultimately, in all the relevant literature, the impacts of an airport are divided into airside and landside components.¹³ Greer, F., Rakas, J., Horvath, A. Airports and environmental sustainability: a comprehensive review. Environmental Research Letters, 15, 103007 (2020). The landside components include, among other things, that the airports also run their generators predominantly on carbon fuels. This fuel is also used at airports for heating boilers, catering, or cogeneration power plants or vehicles.¹⁴ Alba, S. A. & Manana, M. Energy Research in Airports: A Review. Energies, 9(5), 349. (2016). However, the even greater energy demand at an airport is electricity. Electricity is needed to power all the systems and facilities required for safe flight operations. Airports usually obtain this electricity from the public power grid and it is provided by a local energy supply company. In addition, there is also the possibility of producing a certain amount of electricity directly on the airport premises through small wind turbines or solar panels.¹⁵ Alba, S. A. & Manana, M. Energy Research in Airports: A Review. Energies, 9(5), 349. (2016).

2.1.1  Emissions

In terms of CO2 emissions, the aviation sector is showing an upward trend. In the period from 2010 to 2018, the sector’s CO2 emissions increased by 4-5% each year. In 2018, this resulted in a total of 1.04 million tons of CO2 emissions, which accounted for approximately 2.8% of global CO2 emissions and 1.9 % of global greenhouse gas emissions.¹⁶ Ellerbeck, S. World Economic Forum, The aviation sector wants to reach net zero by 2050. How will it do it? https://www.weforum.org/agenda/2022/12/aviation-net-zero-emissions/ (2022). Greenhouse gas emissions are a broad term and include not only CO2 emissions but also all other greenhouse gases. Due to the Corona pandemic, global emissions caused by aviation in 2022 were “only” 0.78 Gt CO2. But with a rising trend again.¹⁷ International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023). In this statistic, passenger air travel, freight and military operations were counted as aviation emissions.¹⁸ Ellerbeck, S. World Economic Forum, The aviation sector wants to reach net zero by 2050. How will it do it? https://www.weforum.org/agenda/2022/12/aviation-net-zero-emissions/ (2022). Of this relatively small global contribution, more than 90% of carbon emissions come from the commercial operation of large aircraft carrying more than 100 passengers per flight.¹⁹ Ciliberti, D., Dellaa Vecchia, P., Memmolo, V., Nicolosi, F., Wortmann, G. & Ricci, F. The Enabling Technologies for a Quasi-Zero Emissions Commuter Aircraft. Aerospace, 9, 319. (2022).

Figure 1 Aviation’s Global CO emissions from 2010-2022 (Data from IEA²⁰ International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport  (2023). )

Flights can generally be categorized as domestic or international. International flights account for 60% of CO2 emissions and domestic flights for only 40%.²¹ Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023). During the Corona pandemic, there was an interim decline in annual aviation and aerospace emissions due to various travel restrictions. For example, in the period from 2019 to 2021, the number of international passengers decreased by 27%. After the restrictions were lifted, the pre-pandemic trend continued.²² Colak, O., Enoch, M. & Morton, Craig. Airport business models and the COVID-19 pandemic: An exploration of the UK case study. Journal of Air Transport Management, Volume 108, 102337 (2023) The number of flights alone from 2020 to 2021 increased from 4.12 million to 5.07 million, according to the European Aviation Environmental Report (2022). In 2019, before the pandemic, there were 9.25 million flights, according to the report.²³ European Union Aviation Safety Agency. European Aviation Environmental Report 2022 (2023). Although the figures only reflect arriving and departing flights from the EU, it illustrates the rising trend in the use of aircraft as a means of transport.

However, the above figures for CO2 emissions, which are used in the literature at large, present the problem that they do not cover all the emissions of the entire industry. Greer et al. (2020) state that the construction and operation of an airport and the manufacturing part are not taken into account. Greer et al. (2020) also find that around 15% of the CO2 emissions generated in connection with flying and the operation of an airport can be attributed to the construction and operation of the airport. This 15% is rarely taken into account in the literature.²⁴ Greer, F., Rakas, J., Horvath, A. Airports and environmental sustainability: a comprehensive review. Environmental Research Letters, 15, 103007 (2020). The industry is aware of both the negative impact of emissions and the current trend. The players of the industry set themselves climate targets to reduce the impact on the environment in the long term. One of the goals is that the industry should achieve net zero emissions by 2050, and in the period 2070-2100, all greenhouse gas emissions should also reach net zero.²⁵ Bergero, C., Gosnell, G., Gielen, D. et al. Pathways to net-zero emissions from aviation. Nature Sustainability 6, pp. 404–414 (2023).

To be able to better measure the impact of individual fuels, the aerospace industry very often uses life cycle assessment (LCA). In a nutshell, LCA is a sustainable framework that is intended to show the effects of a particular process or product on the environment.²⁶ Hadded, F., Jagtap, S., Pagone, E. & Salonitis, K. Sustainability Assessment of Aerospace Manufacturing: An LCA-Based Framework. Global Conference on Sustainable Manufacturing, : Manufacturing Driving Circular Economy pp. 712-720 (2023) For more detailed information about the framework life cycle assessment, please read the wiki article about the framework on our website. Because the framework is very universally applicable, analyses can be found for all sub-sectors of industry. LCA is most often used for the analysis of alternative fuels or for the materials that are being used during manufacturing In addition to the classic LCA method, the life cycle costing (LCC) method is often used in the field of sustainable space engineering. This method is very similar to the classic LCA but focuses more on the influence of the costs and savings that processes or products have on environmental performance.²⁷ Harris, T., Landis, A. Space Sustainability Engineering: Quantitative Tools and Methods for Space Applications. 2019 IEEE Aerospace Conference (2019).

Other standards used in the aerospace industry to measure sustainability are the Global Reporting Initiative (GRI) and the Dow Jones Sustainability Index. The two standards just mentioned are mainly used by large aircraft manufacturing firms such as Airbus, Lockheed Martin Corporation, and Hindustan Aeronautics Limited.²⁸ Raj, A. & Srivastava, S. K. Sustainability performance assessment of an aircraft manufacturing firm. Benchmarking: An International Journal, 25(5), pp. 1500-1527. (2018). GRI is, in short, an organization that has published sustainable guidelines. With these guidelines, which became a standard in 2008, a basis was created to make corporate sustainability reporting more comparable and to create an international standard for reporting.²⁹ Petera, P., Wagner, J. Global Reporting Initiative (GRI) and its Reflections in the Literature. European Financial and Accounting Journal, Vol. 10, Iss. , pp. 13-32. (2015).

2.1.1  Supply Chain Aircraft

In addition to the fuels used and the resulting emissions, there are other negative environmental impact factors in the aviation and aerospace industry. The complete “life cycle” of an aircraft, from the extraction of the basic materials for the construction of the aircraft or components to the scrapping of the aircraft, can be considered and various effects on the environment can be found.³⁰ Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).

Before an aircraft can be built, various materials are needed that either have to be mined or processed and do not come from recycled materials. These include metal components such as titanium, nickel, and aluminum, but also materials that are needed for the board’s electronics, such as lithium for energy storage, graphite, and cobalt. In addition to these metals and other materials, the construction of an aircraft also requires a lot of wood, plastic, and rubber in various forms. During the processing of the raw materials alone, the aerospace industry produces an estimated 2.3 billion tons of waste per year in the USA and Europe alone.³¹ Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).

In addition to the processing of raw materials, aircraft manufacturing processes also have an impact on the environment. The impacts can be divided into four categories: acidification (AP), eutrophication (EP), climate change (GWP), and the category smog (POCP). The individual categories provide information on the emissions of sulfur dioxide (AP), phosphate (EP), carbon dioxide (GWP), and ethene (POCP), which together have a negative impact on the environment. An aircraft consists of various components, such as the fuselage, the wings, the electronics or the engines, and many more. During the production of the respective components, different amounts of the above-mentioned substances are released. However, it can be said that the construction of the engines, wings, and fuselage has the highest impact in all categories. The manufacturing of aircrafts leads to 9.46 ∙10³ kg sulfur (AP), 7.05 ∙10³ kg phosphate (EP), 2.10 ∙10⁶ kg carbon dioxide, and 6.43∙102 kg ethene (POCP) ³² Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).

Many alloys and metals are needed for the construction of aircraft components. The alloys with the greatest environmental impact are tantalum, niobium, aluminum, titanium, and nickel.³³ Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022). In the case of titanium alloys, for example, the greatest impact comes from the use of titanium-molybdenum alloys, which are used because of their heat resistance.³⁴ Soundararajan, S. R., Vishnu, J., Manivasagam, G. & Muktinutalapati, N. R. Processing of beta titanium alloys for aerospace and biomedical applications. Titanium Alloys: Novel Aspects of Their Manufacturing and Processing. (2019). The main driver is the processing of molybdenum. During reprocessing, a large amount of nitrate is released. The nitrate released poses a potential threat to the water ecosystem, which in the worst case can lead to the eutrophication of rivers or lakes.³⁵ Nuss, P. & Eckelman, M. J. Life Cycle Assessment of Metals: A Scientific Synthesis. PLoS ONE 9(7): e101298 (2014)

Generally, the processing of all the required metals and components leads to a high energy demand. Aluminum has the largest share of this. This energy demand leads to CO2 emissions and contributes to air pollution and global warming. In addition to metals, many carbon fiber composites are also used in the aerospace industry in manufacturing processes in all sectors. However, these components have a poor greenhouse gas footprint during processing and further demonstrate the industry’s dependence on fossil fuels. This is because a high proportion of crude oil is required for the production of carbon fiber composites.³⁶ Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).

To be able to measure sustainability during production, various frameworks are used in the aerospace industry. Sustainability performance is influenced by three fundamental dimensions: environmental, economic, and social. These can be further broken down into, for example, raw materials, choice of suppliers, manufacturing, maintenance, etc. A possible framework to measure this is the Fuzzy Performance Important Index (FPII) and the use of the Fuzzy Best Worst Method (FBWM).  With the FPII, companies can identify weak-performing attributes.³⁷ Raj, A. & Srivastava, S. K. Sustainability performance assessment of an aircraft manufacturing firm. Benchmarking: An International Journal, 25(5), pp. 1500-1527. (2018). In the Fuzzy Best Worst Method, all potential possible decisions are evaluated based on criteria and then classified.³⁸ Xu, Y., Zhu, X., Wen, X. & Herrera-Viedma, E. Fuzzy best-worst method and its application in initial water rights allocation. Applied Soft Computing, Volume 101. (2021)

Over time, each aircraft will reach the end of its product life cycle. It is estimated that between 10,000 and 15,000 aircraft will be retired in the coming years. This number may increase as oil and fuel prices rise and aircraft may have to be retired earlier than planned to save money.³⁹ Keivanpour, S. & Ait Kadi, D. End of life aircrafts recovery and green supply chain (a conceptual framework for addressing opportunities and challenges). Management Research Review, 38,10, pp. 1098-1124. (2015). The average age of passenger aircraft when they are decommissioned is between 25-28 years and for freighters between 31-38 years. An aircraft has about 350,00 valuable components at the time of decommissioning and about 90% of a decommissioned aircraft can be reused or recycled.⁴⁰ Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023). However, despite the high proportion of reusable components, the decommissioning of an aircraft also hurts the environment. On the one hand, 10% of non-reusable parts remain as waste, and on the other hand, the decommissioning process leads to environmental and air pollution, which negatively affects human health and biodiversity.⁴¹ The United State Environmental Protection Agency. Aerospace Manufacturing Sector–Pollution Prevention (P2) Opportunities. https://www.epa.gov/toxics-release-inventory-tri-program/aerospace-manufacturing-sector-pollution-prevention-p2 (2022).

2.2 Comparative analysis of sustainability impacts

In the following, we will compare and rank the sustainable impact of the aerospace industry with other comparable industries. Due to the complexity of the aerospace industry, there is no all-encompassing industry that is fully comparable. Despite this, the sub-sectors can be compared very well with other sectors, for example in the area of CO2 emissions, it is useful to compare aviation and road transport.

According to the International Energy Agency, the entire transport sector was responsible for emissions of almost 8 Gt CO2 in 2022.⁴² International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023). This accounts for just over 20% of global CO2 emissions.⁴³ Statista. Verteilung der CO2-Emissionen weltweit nach Sektor bis 2021. https://de.statista.com/statistik/daten/studie/167957/umfrage/verteilung-der-co-emissionen-weltweit-nach-bereich/ (2022). As mentioned above, the aviation sector was responsible for approx. 0.78 Gt CO2 in that year and thus, in purely quantitative terms, aviation is responsible for approx. 11% of CO2 emissions. For the road transport sector, the picture is much different in terms of contributors. With approx. 5.87 Gt co2 and a percentage share of approx. 74%, the sector is the clear leader in the transport sector in terms of CO2 emissions.⁴⁴ International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023). This percentage difference is primarily due to the number of vehicles in the world. There are far more cars or trucks in the world than there are planes. By way of comparison, there are an estimated 1 billion cars in the world ⁴⁵ Gössling, S. Why cities need to take road space from cars – and how this could be done. Journal of Urban Design, Volume 25, Issue 4 pp. 443-448. (2020). , whereas in 2022 there were just 42 million flights worldwide⁴⁶ Statista. Anzahl der Flüge in der weltweiten Luftfahrt von 2014 bis 2022(in Millionen). https://de.statista.com/statistik/daten/studie/411620/umfrage/anzahl-der-weltweiten-fluege/ (2023). and it is forecast that by 2041 there will be just 3610 cargo aircraft in use.⁴⁷ Statista. Statistiken zur weltweiten Luftfahrt. https://de.statista.com/themen/4313/weltweite-luftfahrt/#topicOverview (2023). This huge difference in numbers and the proportionate CO2 emissions generated by the aerospace industry make it clear that a single aircraft generates a relatively large amount of emissions. For example, a flight for a family of four from Berlin to Barcelona has a carbon footprint of 2.2 tons. This single flight alone generates more emissions than a petrol or diesel car would cause in an entire year.⁴⁸ Carroll, J., Brazil, W. Howard, M. & Denny, E. Imperfect emissions information during flight choices and the role of  CO2 labeling. Renewable and Sustainable Energy Reviews,  Volume 165, 112508. (2022).  

In the field of freight transport, air transport has the worst overall CO2 footprint. We have already looked at the relationship between air and road transport. In the comparison between aviation and transport by ship, air transport does not fare much better. Although shipping caused 0.89 Gt CO2 in 2022 and thus a slightly higher value than aviation, a single ship can transport far more goods than a single aircraft.⁴⁹ International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023). This means that transport by ship produces about the same amount of emissions but can carry far more passengers and goods than aviation.

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Furthermore, another difference between aircraft emissions and the emissions of all other means of transport, be it cars, ships, or trains, is the place where the greenhouse gases are released. In the case of ships, cars, and railways, the emissions take place close to the ground, but in the case of aircraft, starting with take-off and landing, most of the emissions take place at altitudes of around 9150-13,000 km above sea level.⁵⁰ Samuels MPThe effects of flight and altitudeArchives of Disease in Childhood;89:448-455. (2004). Thus, aircraft emissions occur directly at the place, the atmosphere, and the ozone layer, where they can have the greatest possible negative impact on the environment. Furthermore, unlike the other transport options, the emitted gases do not have to make their way there first.

3 Sustainability Strategies and Measures

The aerospace industry plays a significant role in shaping the modern world by enabling global connectivity, scientific exploration, and technological advancements. However, the industry’s rapid growth has raised concerns about its environmental impact and sustainability. In response to these challenges, the development and implementation of sustainability strategies in the aerospace sector have gained considerable attention. These strategies aim to mitigate the industry’s ecological footprint, promote resource efficiency, and foster long-term environmental stewardship. By adopting sustainable practices, the aerospace industry seeks to balance technological progress with responsible environmental management.

However, implementing sustainability strategies in aerospace is not without its challenges. The industry faces unique complexities due to the nature of its operations, including long lifecycles, technological advancements, and safety considerations. Balancing environmental concerns with safety and innovation is a delicate task that requires careful planning and collaboration among industry players, regulators, and stakeholders. Moreover, sustainable practices must be economically viable to ensure long-term feasibility and industry-wide adoption. To overcome these challenges, the aerospace sector has embraced a range of sustainability strategies. These strategies encompass various aspects, including aircraft design and manufacturing processes, fuel efficiency improvements, alternative fuels, and alternative engines. Collaboration between aerospace companies, research institutions, and government bodies is vital to accelerate the implementation of sustainable practices and drive technological advancements.

3.1 More fuel-efficient aircraft

The first strategy is an evolution rather than a revolution.  Aircraft manufacturers such as Boeing or Airbus, in collaboration with engine manufacturers, are developing more and more fuel-efficient aircraft. Fuel is one of the biggest costs for an airline. Besides the aspect of sustainability, there is also an economic incentive for the airlines to buy new fuel-efficient aircraft. This in turn creates technical competition on the manufacturer’s side. The increase in efficiency is mostly achieved through two aspects. First is further development of the engines. Second is the use of “new” materials in aircraft manufacturing and new or more efficient aircraft designs. Generally, the use of carbon fiber composite contributes to a more fuel-efficient fleet for the manufacturers. The use of carbon fiber composite decreases the weight of the aircraft and with that, increases the fuel efficiency. In modern aircrafts like the Airbus A 350 XWB more than half of the aircraft is built with Carbon fiber composite.⁵¹ Airbus. Composites: Airbus continues to shape the future. Airbus. https://www.airbus.com/en/newsroom/news/2017-08-composites-airbus-continues-to-shape-the-future (2017).

The three most important engine manufacturers are CFM International, Pratt & Whitney and Rolls-Royce. Together these three account for 93 Percent global engine deliveries.

3.2 Sustainable aviation fuels

The second measure taken by aircraft manufacturers and Fuel producers is the development and introduction of sustainable aviation fuels. So far, there is no general definition of what a sustainable aviation fuel is. Nevertheless, this term is usually used to describe a drop-in alternative for kerosene, which is obtained from a range of raw materials.⁵² Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022). Drop-in kerosene alternatives stand in contrast to other forms of propulsion, such as hydrogen or electric powered planes.

The main advantage of sustainable aviation fuels over other alternatives like hydrogen or electric powered planes, is their relative ease of use. The reason for this lies in their functional similarity to conventional kerosene, which is derived from fossil fuels. This equality means that there is no need for major investment in new infrastructure or modifications to either the airport or the aircraft itself. In addition, there is also the possibility to use a blend of sustainable aviation fuel and conventional aviation fuel.⁵³ Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).

Currently, sustainable aviation fuels or low-carbon fuel accounts for a market share of just 0.1 percent.⁵⁴ Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020). At the moment, only a small production capacity is available for SAF. This is due to several reasons. Firstly, the technology for producing these sustainable aviation fuels is not yet fully developed. Secondly, the availability of the required raw materials is limited in the quantity it is needed.⁵⁵ Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022). These reasons have led to the current price that airlines must pay for SAF per ton being 1.5 to 6 times higher than the price for a ton of conventional fuel.⁵⁶ ESA. Current landscape and future of SAF industry. ESA https://www.easa.europa.eu/eco/eaer/topics/sustainable-aviation-fuels/current-landscape-future-saf-industry (no date). The cost of fuel makes up a large part of the operating costs for airlines.⁵⁷ MRAZOVA, Maria. Innovations, technology and efficiency shaping the aerospace environment P.92. The aviation market is a competitive market which is under strong price pressure. This is especially true in the low-cost sector, where companies such as Ryanair or Southwest Airlines are located. In such a competitive environment, the prices demanded for sustainable aviation fuels cannot be paid, especially when cheaper alternatives in the form of conventional fuel exist. This would result in a disadvantage compared to their competitors. Therefore, a reduction in the price of sustainable aviation fuels is of paramount importance for further dissemination.

3.3 Hydrogen

As noted above, the use of hydrogen as a fuel for aircraft is another more sustainable approach. As in other sectors such as the automotive industry, the use of hydrogen is being worked on and is seen as a partial solution to more environmentally friendly flying. This is due to the fact that when hydrogen is combusted, no air pollutants or greenhouse gases are produced. Nevertheless, the use of hydrogen is only climate-neutral if renewable energy is used in its production.⁵⁸ Die Bundesregierung.  Nationale Wasserstoffstrategie, Energie aus klimafreundlichem Gas. Bundesregierung https://www.bundesregierung.de/breg-de/schwerpunkte/klimaschutz/wasserstoff-technologie-1732248#:~:text=Das%20Besondere%3A%20Dabei%20entstehen%20keine,Windkraftanlagen%20oder%20Solarmodulen%20erzeugt%20wird  (2023).

In addition to the advantage of the climate-neutral combustion of hydrogen, there are also properties that speak against a sufficient spread of hydrogen in aviation. These are a result of the technical characteristics of hydrogen. In comparison to conventional aviation fuel, hydrogen possesses a higher gravimetric energy density and the volumetric energy density is lower.⁵⁹ Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020). This has two main consequences for the use of hydrogen in aviation. First, through the low volumetric energy density, the fuel capacity is going to be limited. This is problematic for long haul routes operated by airlines, who are more fuel intense.⁶⁰ Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022). The second consequence is the need of a slightly different airplane. This is also the result of the lower volumetric energy density of hydrogen in comparison to conventional aviation Fuel. To ensure safe operation with hydrogen, the aircraft must be optimized for the additional weight that hydrogen adds.⁶¹ Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).

3.4 Electric powered aircrafts

In addition to the use of sustainable aviation fuels and hydrogen to power aircraft, efforts to electrify aviation are continuing. There are currently two approaches to using electricity to power an aircraft. The first approach is a hybrid system. This system combines an electric motor and a turbofan.⁶² bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022). The second system uses a fully electric solution, where no further conventional engine is used to generate the power for the aircraft.⁶³ bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).

Electric powered aircraft possess the same sustainable advantages as electric cars. The operation of electric cars or electric airplanes does not emit any environmentally harmful emissions. However, it must be considered that the production of the electricity used in the operation of the aircraft must be generated in an environmentally friendly manner, in order to be sustainable. It must be said that only a fully electric solution will enable truly sustainable operation of an aircraft. Furthermore, electric power aircrafts have the advantage of a quitter operation compared to conventional aircrafts.

Although, there is a sustainable benefit to using electric powered aircraft, there are technical issues that limit their use commercially. The main problem is the need for a battery if an aircraft is to be powered by electricity. Electricity stored in a battery has a much lower energy density compared to conventional aviation fuel. For this to work, an aircraft must carry more weight to fly the same distance. For example, in order to carry the energy contained in the tank of an Airbus A 380 in electricity, an additional weight would have to be carried by current batteries. In this case, the weight of those batteries would be approximately 38 times the permissible take-off weight of that aircraft type.⁶⁴ Caset, f. Boussauw, k. & Storme, T. Meet & fly: Sustainable transport academics and the elephant in the room. Journal of Transport Geography, 70, 64-67 (2018). Additionally, a conventional aircraft burns fuel while its flying. This means it reduces its weight over the time span of its flight. Due to this, the aircraft increases fuel efficiency over the length of the flight. In comparison the weight of the battery used to store the electricity for the flight will remain constant over the time spanned in the air.⁶⁵ Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 4, (2022).

Another technical issue is the need for a new airframe design, that is specially developed for the needs of electric aviation. Right now, aircrafts are not designed for the needs of electric power, but rather for conventional engines. There are two approaches to solving this problem. The first one is to use conventional tube and wing aircraft designs.⁶⁶ bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022). Secondly there is the approach to use a radical new design. These new designs that are develop by different manufactures, are adapted to the conditions of electrical energy.⁶⁷ Wu, j, Gao, F, Li, S & Yang, F. Conceptual Design and Optimization of Distributed Electric Propulsion General Aviation Aircraft. Aerospace 10, 387 (2023). An example for this is the Airbus Vahana. This is a single seat eVTOL with a radical new design approach.⁶⁸ Airbus. Vahana: Our single-seat eVTOL demonstrator. Airbus. https://www.airbus.com/en/innovation/low-carbon-aviation/urban-air-mobility/cityairbus-nextgen/vahana  (No date).

One more problem electric aviation is facing is the current infrastructure that is used around the globe. Currently Airports are built for conventional Aircrafts who uses Jet fuel to operate. This is relatively easy to do. For this, usually only one tank and one tanker vehicle are needed. This takes the fuel to the aircraft where it is then refueled. The process of refueling naturally takes time, normally around 15 to 20 minutes.⁶⁹ Joshi, G. How Is An Aircraft Refuelled? Refuelling an aircraft has its own process, and we take a look at how it’s done. Simple Flying. https://simpleflying.com/how-is-an-aircraft-refuled/ (2022). In order to “refuel” an electric aircraft there are two possible methods. One solution is to charge the aircraft. The other is to swap the battery.⁷⁰ van Oosterom, S & Mitici, M. Optimizing the battery charging and swapping infrastructure for electric short-hauk aircraft – the case of electric flight in Norway. Transport Research Part C 155 (2023). Both cases possess their own pros and cons. Nevertheless, each approach requires the existing infrastructure to be modified.

Due to the technical limitations that still exist at the moment, it can be assumed that the electrification of aviation will not prevail in the long-haul sector. However, there is a use for electric aircraft in the short-haul sector. In this area, the limitation in range is not a significant issue. Furthermore, the difference in speed between an electric and a jet aircraft is mainly related to short distances.

3.5 Boeing and Airbus

Boeing and Airbus are the world’s largest aircraft manufacturers. Together, the two aircraft manufacturers delivered 1141 aircraft to their customers in 2022.⁷¹ Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022). ⁷² Boeing. Boeing Reports Commercial Orders and Deliveries for 2022. Boeing. https://investors.boeing.com/investors/news/press-release-details/2023/Boeing-Reports-Commercial-Orders-and-Deliveries-for-2022/default.aspx (2023). Both companies need to improve the sustainability of their products in the wake of the requirements that airlines are placing on the sustainability of their fleets. For the airlines, there are two main reasons. The first is to further reduce costs. This is achieved by increasing the efficiency of the aircraft operated. Secondly, an environmentally friendly image is a decisive marketing argument for the airlines. In addition, there are increasing numbers of regulations on what aircraft must meet in order to be allowed to operate. In order to offer a more environmentally sustainable product range, both aircraft manufacturers are pursuing a sustainability strategy.

3.5.1 Boeing

The sustainability strategy of Boeing is based on four key areas. These areas are Fleet Renewal, Operational Efficiency, Renewable Energy and Advance in Technology.⁷³ Boeing. Sustainability Report: Sustainable Aerospace Together. (2022). The first of the four areas is the renewal of the operational fleet. The use of a newer and more sustainable fleet, mainly achieved through fuel efficiency, can lead to a reduction in greenhouse gas emissions. However, it must be mentioned that a renewal of the fleet is associated with considerable costs, which exist on the side of the airlines. The second area is Operational Efficiency. Operational efficiency is to be achieved through improved processes in flight operations. With the help of improved data analysis, for example, a better flight route can be created, which leads to lower fuel consumption. The third point in Boeing’s sustainability strategy is the use of sustainable energy. The use of sustainable energy in production and operations ensures a reduction in emissions that are harmful to the environment. The fourth area is the largest. Boeing wants to adapt its line to function using more modern technology.  In doing so, they are pursuing the aforementioned aspects. On the one hand, Boeing is focusing on an improved and more efficient design of the aircraft produced, as well as on the materials used in production. In addition to improving existing technology, Boeing is pursuing the use of sustainable aviation fuels. In addition to the use of SAF, Boeing sees the future of green flying in the utilization of hydrogen for aircraft operation.⁷⁴ Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).

3.5.2 Airbus

Airbus is committed to the UN SDGs.⁷⁵ Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022). In order to achieve the goals for more sustainable flying, Airbus is like Boeing also focusing on the use of modern aircrafts and the improvement of aircraft designs. Furthermore, Airbus continues to improve on the use of sustainable aviation fuels in aircraft produced by them.⁷⁶ Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022). However, Airbus sees the use of an alternative fuel as a long-term solution for sustainable aviation. For them, the use of hydrogen in aviation is the future. There for Airbus is investing in several partners in order to scale up the production of hydrogen. In addition, Airbus is also planning further innovations in its core segment. With Airbus’ ZEROe initiative, for example, the goal of developing a commercial aircraft by 2035 has been set.⁷⁷ Airbus. ZEROe: Towards the world’s first hydrogen-powered commercial aircraft. Airbus. https://www.airbus.com/en/innovation/low-carbon-aviation/hydrogen/zeroe (No date).

4 Drivers and Barriers

4.1 Drivers

4.1.1 Firm-Internal Drivers

One key aspect which can be make or break for corporate sustainability within and beyond the aerospace industry is corporate governance.⁷⁸ Crifo, P., Escrig-Olmedo, E. & Mottis, N. Corporate governance as a key driver of corporate sustainability in France: the role of board members and investor relations. Journal of Business Ethics 159, 1127–1146 (2018). Corporate governance refers to “the structures that specify the rights and responsibilities among the parties with a stake in the firm as well as the configurations of organizational processes that affect both financial and nonfinancial firm-level outcomes.”⁷⁹ Zaman, R., Jain, T., Samara, G. & Jamali, D. Corporate governance meets corporate social responsibility: Mapping the interface. Business & Society 61, 690–752 (2020). Companies’ governing bodies determine the values and goals of firms and can thereby play a key role in an organization’s decision to operate sustainably or not. Several studies have shown how, across industries, the size, level of diversity, and CEO compensation systems can play a defining role in the implementation of sustainability at the firm level. This is also true within the aerospace industry.⁸⁰ Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021). Larger boards of directors or other corporate governing bodies can be generally more effective due to the increased number of voices and contributions, which are said to decrease opportunistic behavior.⁸¹ Gangi, F., Daniele, L. M. & Varrone, N. How do corporate environmental policy and corporate reputation affect risk‐adjusted financial performance? Business Strategy and the Environment 29, 1975–1991 (2020). The top 5 firms in the aerospace industry are General Electric (GE), Northrop Grumman, Lockheed Martin, Boeing, and Airbus. As of August 2023, among these firms, Lockheed Martin and Boeing are tied for the largest boards, with 13 members each.⁸² Lockheed Martin. Board of Directors. Lockheed Martin https://www.lockheedmartin.com/en-us/who-we-are/leadership-governance/board-of-directors.html (2023). ⁸³ Boeing. Corporate Governance. Boeing https://www.boeing.com/company/general-info/corporate-governance.page (2023). GE comes in last with 10 members.⁸⁴ General Electric. GE Board of Directors. GE Governance https://www.ge.com/investor-relations/governance (2023). Airbus middles across board indicators.⁸⁵ Airbus. Board and Board Committees. Airbus https://www.airbus.com/en/our-governance/board-and-board-committees (2023). Gender diversity is also a documented driver of environmentally positive action by firms.⁸⁶ Khatib, S. F. A., Abdullah, D. F., Elamer, A. A. & Abueid, R. Nudging toward diversity in the boardroom: A systematic literature review of board diversity of financial institutions. Business Strategy and the Environment 30, 985–1002 (2020). Among these same 5 firms, an average of just above 36% of board membership is made up by women. Northrop Grumman has achieved the highest rate of female membership at 46%.⁸⁷ Northrop Grumman. Company Leadership. Northrop Grumman https://www.northropgrumman.com/who-we-are/leadership (2023). In contrast, Lockheed Martin and Boeing are tied in last with 31%. This means that each of these boards does include several voices with at least some gender diversity, which may help to push them towards improvements in their future sustainability performance.

Innovation is another central driver of sustainability within firms. Innovation is often carried out in order to meet the needs of aerospace firms in terms of materials or fuel efficiency. Product-related innovation aimed at achieving environmental sustainability is known as green product innovation (GPI). GPI occurs in companies that seek to make themselves more competitive through proprietary development of technologies that will become necessary in the sustainable economy of the future. Innovations in this direction set companies apart as GPI leaders in the industry, making them more attractive for environmentally conscious consumers. Specifically in the aerospace sector, GPI is a key driver of both sustainability and profitability, making it an effective solution for driving transformation in the industry.⁸⁸ Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).

Risk Aversion can be another internal driver of sustainability. Aerospace companies operate in an industry that has maintained relative stability through the use of long-lived products and tried and tested technologies. These are companies that seek to avoid risks wherever possible and tend to prefer to apply the same strategies over time.⁸⁹ Lewis, A. & Loebbaka, J. Managing future and emergent strategy decay in the commercial aerospace industry. Business Strategy Series 9, 147–156 (2008). Thus, they recognize that environmental risks, including regulatory fines and reputation damage due to environmental incidents, can impact their operations and financial performance. Especially as issues arise within the supply chain and in the face of resource scarcity and the rising costs of key materials, firms cannot ignore the ways unsustainable behaviors and practices can be harmful. Other risks such as fuel price volatility can be mitigated by the use of alternative fuels. Firms that are aware of and maybe even effected by such risks seek out sustainability and undertake the requisite measures to mitigate them.

In many firms, cost reduction plays a key role in decision making. In such firms within the aerospace industry, especially among aviation operators, there is strong motivation to achieve efficiency of materials and energy. Improving fuel efficiency can be a cost-reducing measure as planes and other vehicles require less fuel.⁹⁰ Lim, M., Luckert, M. K. & Qiu, F. Economic opportunities and challenges in biojet production: A literature review and analysis. Biomass & Bioenergy 170, 106727 (2023). Any reduction in the need for fuel can be a driver of sustainability in the industry given the high-emitting nature of aviation fuels regardless of the motivation behind it. It also seems that efficiency is one of the best ways for aerospace firms to begin their sustainability transitions.⁹¹ Wu, P.-J. & Yang, C.-K. Sustainable development in aviation logistics: Successful drivers and business strategies. Business Strategy and the Environment 30, 3763–3771 (2021).

4.1.2. Firm-External Drivers

Although there are some drivers of sustainability within firms, it is often external factors that play a deciding role in their contributions to sustainability. By far one of the most instrumental of these drivers is both political and economic in nature, namely, public policy.⁹² Qiu, R., Hou, S., Chen, X. & Meng, Z. Green aviation industry sustainable development towards an integrated support system. Business Strategy and the Environment 30, 2441–2452 (2021). There are sustainability regulations at the international, national, and sometimes the local level which are broad and not aimed at specific sectors. There are two key political and economic frameworks regulating sustainability in the aerospace industry at the international level: the Kyoto Protocol (KP) and the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).

The Kyoto Protocol is an agreement which was adopted in 1997 by the members of the International Civil Aviation Organization (ICAO), a UN agency made up of 191 member states specializing in aviation-related issues. It is aimed at addressing climate change by setting binding targets for industrialized countries to reduce their greenhouse gas emissions. The agreement did not list specific emissions reduction targets for aerospace or even for aviation on an international level, although targets were set for domestic aviation. The Protocol served as the basis for the future development of sustainability policy aimed at the aerospace and aviation sector, namely CORSIA.

CORSIA was created in order to address emissions specifically in the aviation industry and incentivize a reduction in those emissions on an international level. The agreement was developed by the ICAO and was adopted in 2016, and although compliance is not set to be mandatory until 2027, many countries began participating starting in 2020. CORSIA is a market-based scheme which requires aviation operators to purchase offsets or carbon credits to cover their emissions so that the industry can effectively achieve carbon neutral growth starting from 2020. This system requires extensive monitoring and reporting efforts both for the industry itself and for national-level regulators which will be tasked with ensuring that the scheme works correctly and can achieve its goal. In order to continue improving sustainability, CORSIA goes beyond just requiring carbon trading. The agreement also includes provisions supporting the development and implementation of SAFs as the member states recognize the key role that fuels play in the industry’s high emissions. By pushing green innovation in this context, the aviation sector will be in a better position to achieve its goal of carbon neutral growth by lowering its overall emissions rather than solely through offsetting them. ⁹³ Scheelhaase, J., Maertens, S., Grimme, W. & Jung, M. H. EU ETS versus CORSIA – A critical assessment of two approaches to limit air transport’s CO 2 emissions by market-based measures. Journal of Air Transport Management 67, 55–62 (2018). Studies have shown that CORSIA does actively promote emissions reduction and that if further measures are taken, these benefits will increase.⁹⁴ Scheelhaase, J. & Maertens, S. How to improve the global ‘Carbon Offsetting and Reduction Scheme for International Aviation’ (CORSIA)? Transportation Research Procedia 51, 108–117 (2020).

Regardless of sector, demand for sustainability has increased over the last several years, with special focus put on aviation and the aerospace industry as a whole. Several social movements have arisen asking consumers to make decisions based on the long-term effects of their actions, rather than the short-term ones. One particular social driver of rising demand for sustainability in aviation is flight shame. This phenomenon was first documented in Sweden and is more visible in Scandinavia, although its effects do appear to be spreading throughout Europe. In these cases, individuals fear being ostracized or experiencing other negative social effects for participating in traditional air travel.⁹⁵ Mkono, M. Eco-anxiety and the flight shaming movement: implications for tourism. Journal of Tourism Futures 6, 223–226 (2020). This fear and the shame associated with flying is so extreme that it can drive individuals to stop using air travel altogether. Similarly, eco-anxiety arising from an awareness of the effects of the use of fossil fuels, air travel, and other environmentally destructive activities can push people to stop participating or to demand rapid improvements in sustainability to do so. Even where fear is not a key motivator, this awareness of sustainability issues has increased to the point where it has become difficult for individuals or companies to ignore. As aerospace firms and operators become aware of these phenomena, they must act to address them, to ensure that future generations will be willing to take advantage of their products and services at all.

4.2 Barriers

4.2.1 Firm-Internal Barriers

Despite the many drivers of sustainability in the aerospace industry, there are still several barriers. As previously mentioned, corporate governance plays a key role in sustainability efforts in the aerospace industry. This means that those firms with small governing bodies and little diversity are less likely to see sustainability as a priority or to act sustainably. This often occurs in conjunction with the application of the shareholder perspective rather than the stakeholder perspective.⁹⁶ Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021). Here, aerospace firms focus only on profitability and satisfying shareholders. Given the rise in demand for air-based travel and transport, there is much money to be made from continuing traditional operations. Especially in cases where CEO compensation and profits are not tied with sustainability performance, there is little motivation for leadership to push for increased sustainability measures. Some aerospace companies have overcome this issue simply by including climate performance and CSR in their CEO compensation schemes. For example, Safran ties 11.7% of its CEO’s compensation to sustainability objectives.⁹⁷ Safran Group. Corporate Officer Compensation (2021-2022). Safran Group https://www.safran-group.com/sites/default/files/2022-02/Corporate%20Officer%20Compensation%20%282021-2022%29.pdf (2022). This means that the CEO’s income is directly affected by the company’s ability to achieve its sustainability goals. However, in some cases this does not happen. One way that firms can overcome this lack of motivation on the part of leadership is by pointing to studies and examples of the profitable nature of at least certain types of sustainable processes, especially those concerned with resource and fuel-efficiency. This is true for Rolls-Royce, which ties compensation solely to financial performance.⁹⁸ Rolls-Royce. Director Remuneration Policy 2021. Rolls-Royce https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/annual-report/2021/director-remuneration-policy-2021.pdf (2021). The company has, however, chosen to focus on innovation in order to participate in the “significant commercial opportunity presented by the transition to net zero.”⁹⁹ Rolls-Royce. Annual Report 2021. Rolls-Royce https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/annual-report/2021/ar2021-strategic-report.pdf (2021). In this way, even if the company is oriented toward shareholders rather than stakeholders, they may be able to be convinced that sustainability is in the best interest of those stakeholders.

Although risk aversion can be a driver of sustainability in the aerospace industry, it can also be a barrier. GPI, which typically drives improvements in climate performance, requires massive amounts of time, resources, and funding. In many cases, firms will accept these burdens if they see the end result as being advantageous. However, in the aerospace industry, the burden is high enough and the results are unclear enough that firms may often opt out of pursuing this type of innovation. This is especially true given the risk-averse and safety-oriented nature of the industry.¹⁰⁰ Lewis, A. & Loebbaka, J. Managing future and emergent strategy decay in the commercial aerospace industry. Business Strategy Series 9, 147–156 (2008). Aviation, space flight, and even manufacturing are activities that require extensive know-how, testing, and evidence to be carried out safely. Therefore, the technologies that currently exist took time to become common and regularly used. In most cases, there is strong evidence that the existing systems function well, making the prospect of introducing new products seem potentially threatening as there are many unknowns. The cost of innovation is another major risk to companies as investing in new and untested materials, components, and products may not lead to their successful implementation.¹⁰¹ Gonzalez-Garay, A. et al. Unravelling the potential of sustainable aviation fuels to decarbonise the aviation sector. Energy and Environmental Science 15, 3291–3309 (2022). Although legislation and industry-wide agreements do exist that ask operators to carry out research and development to improve sustainability, often they lack the financial support to effectively incentivize aerospace firms to work extensively on such risky projects.¹⁰² Scheelhaase, J. & Maertens, S. How to improve the global ‘Carbon Offsetting and Reduction Scheme for International Aviation’ (CORSIA)? Transportation Research Procedia 51, 108–117 (2020). One way that firms have overcome some of these risks is by working together across the industry. One bold example of this is an industry partnership between Airbus and CFM International, a joint venture from GE and Safran, working towards development of a flightworthy plane run on hydrogen combustion.¹⁰³ Airbus. At Airbus, hydrogen power gathers pace. https://www.airbus.com/en/newsroom/stories/2023-06-at-airbus-hydrogen-power-gathers-pace (2023). This kind of innovation requires years of development, but the risk is shared across several companies and is therefore somewhat minimized.

4.2.2 External Barriers

There are multiple key firm-external barriers to sustainability in the aerospace industry. First and foremost is the technological barrier that is the industry’s absolute dependence on fossil fuels. Fossil fuels require large amounts of resources and energy to be extracted, and they release heavy levels of carbon and other greenhouse gases during both the extraction and combustion process.¹⁰⁴ Clancy, J. M., Gaffney, F., Deane, P., Curtis, J. & Gallachóir, B. P. Ó. Fossil fuel and CO2 emissions savings on a high renewable electricity system – A single year case study for Ireland. Energy Policy 83, 151–164 (2015). The reality of the aerospace industry is that most vehicles cannot fly using existing SAFs without at least some percentage of traditional fossil fuel sources included in the process. Even innovators such as Airbus only currently have the capacity to make regular flights using biofuels to support 50% of total fuel needs.¹⁰⁵ Airbus. Airbus’ most popular aircraft takes to the skies with 100% sustainable aviation fuel. https://www.airbus.com/en/newsroom/stories/2023-03-airbus-most-popular-aircraft-takes-to-the-skies-with-100-sustainable (2023). These vehicles are extremely heavy and must bear the burden of added cargo and human life, making it necessary that they be durable and sturdy, even as they must be light enough to fly at all. Technology is being developed to solve this issue. Biodiesel and other ‘green’ fossil fuels are the first step being taken towards sustainability; however, it is still in the early stages of application and is not yet used across the industry. Much hope has also been placed in the potential of hydrogen power; however, this technology does not currently exist, and what does exist is in the earliest days of development and is mainly driven by the use of fossil fuels to make the process functional.¹⁰⁶ Tashie-Lewis, B. C. & Nnabuife, S. G. Hydrogen Production, Distribution, Storage and Power Conversion in a Hydrogen Economy – A Technology Review. Chemical Engineering Journal Advances 8, 100172 (2021). Technology is a barrier simply because although it is already actively being included in aerospace firms’ sustainability strategies, much of this technology does not actually exist yet and will require several more years of development and testing to be ready to market on a large scale. 

Recent years have seen an overall rise in demand for air-based travel and logistics.¹⁰⁷ Lim, M., Luckert, M. K. & Qiu, F. Economic opportunities and challenges in biojet production: A literature review and analysis. Biomass & Bioenergy 170, 106727 (2023). This is in part due to the pandemic, which caused a stoppage of travel for a time followed by a huge increase after it ended, as well as an increase in online shopping which has continued until now. Despite rising demand for sustainability, the reality is that there is a large social or socioeconomic barrier to sustainability in the aerospace industry. This barrier is known as the attitude-action gap.¹⁰⁸ McDonald, S., Oates, C., Thyne, M., Timmis, A. & Carlile, C. Flying in the face of environmental concern: why green consumers continue to fly. Journal of Marketing Management 31, 1503–1528 (2015). Many people care about the environment and want to act in an environmentally friendly way, but still choose to fly or shop online from stores across the world, causing air traffic to rise dramatically. There are several reasons for this, including costs which are sometimes lower for air travel than land-based travel, and for products made from less expensive materials but often coming from distant countries, requiring air-based shipping.¹⁰⁹ Schleiden, V. & Neiberger, C. Does sustainability matter? A structural equation model for cross-border online purchasing behaviour. The International Review of Retail, Distribution and Consumer Research 30, 46–67 (2019). Individuals may be interested in traveling using sustainable options, but often, there is a cost increase associated with these options, keeping people from using them, whether due to budget constraints or general financial preferences.¹¹⁰ Hansmann, R. & Binder, C. R. Reducing personal air-travel: Restrictions, options and the role of justifications. Transportation Research Part D-transport and Environment 96, 102859 (2021). Another reason for this discrepancy is social considerations, in which individuals worry that not meeting social expectations, such as flying to visit family members, would be worse individually than the benefit of more sustainable travel.¹¹¹ Schmidt, F., Sidders, A., Czepkiewicz, M., Árnadóttir, Á. & Heinonen, J. ‘I am not a typical flyer’: narratives about the justified or excessive character of international flights in a highly mobile society. Journal of Sustainable Tourism 1–24 (2023). Finally, convenience and consumerism can serve to keep individuals from consuming more sustainable travel options in favor of ubiquitous, well-known, and easy-to-reach options, including traditional fossil-fueled air travel.¹¹² McDonald, S., Oates, C., Thyne, M., Timmis, A. & Carlile, C. Flying in the face of environmental concern: why green consumers continue to fly. Journal of Marketing Management 31, 1503–1528 (2015).

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References

• 1
  United Nations. International Standard Industrial Classification of All Economic Activities ISIC Rev. 3.1. (2002).
• 2
  OECD. “Overview of the aerospace sector: background”, in The Space Economy at a Glance 2007 OECD Publishing, Paris. (2002).
• 3
  He, S., Hipel, K.W. & Kilgour, M. Analyzing market competition between Airbus and Boeing using a duo hierarchical graph model for conflict resolution. Journal of Systems Science and Systems Engineering, Volume 26, pages 683-710 (2017).
• 4
  Jones, M. Boeing vs. Airbus: The Key Reason Why Airbus Stock is Better https://www.nasdaq.com/articles/boeing-vs.-airbus:-the-key-reason-why-airbus-stock-is-better (2023).
• 5
  Statista. Umsatz der weltweit führenden Flugzeughersteller und Zulieferer im Jahr 2022(in Milliarden US-Dollar) https://de.statista.com/statistik/daten/studie/30808/umfrage/umsatz-der-weltweit-fuehrenden-flugzeughersteller/#:~:text=Airbus%20und%20Boeing%20sind%20die,vorn%2C%20was%20die%20Flugzeugauslieferungen%20anbelangt. (2023).
• 6
  Encyclopedia Britannica. Aviation https://www.britannica.com/technology/aviation (2023)
• 7
  Airbus. Non-Financial Information Annual Report (2021).
• 8
  Dias, V.M.R., Jugend, D., de Camargo Fiorini, P., do Amaral Razziono, C. Antonio Paula Pinhero, M. Possibilities for applying the circular economy in the aerospace industry: Practices, opportunities and challenges. Journal of Air Transport Management, Volume 102, 102227 (2022).
• 9
  Franchino, M. Framework for Sustainability in Aerospace: A Proof of Concept on Decision Making and Scenario Comparison. In: Kohl, H., Seliger, G., Dietrich, F. (eds) Manufacturing Driving Circular Economy. GCSM 2022. Lecture Notes in Mechanical Engineering. Springer, Cham. (2023).
• 10
  Abbasi, T., & Abbasi, S. A. Decarbonization of fossil fuels as a strategy to control global warming. Renewable and Sustainable Energy Reviews, 15(4), 1828. (2011).
• 11
  O. Yoro, K. & o. Dadmola, M. CO2 emission sources, greenhouse gases, and the global warming effect. Advances in Carbon Capture Methods, Technologies and Applications. pp. 3-28. (2020).
• 12
  Mishra, S. Is smog innocuous? Air pollution and cardiovascular disease. Indian Heart Journal, Volume 69, Issue 4, pp. 425-429. (2017).
• 13
  Greer, F., Rakas, J., Horvath, A. Airports and environmental sustainability: a comprehensive review. Environmental Research Letters, 15, 103007 (2020).
• 14
  Alba, S. A. & Manana, M. Energy Research in Airports: A Review. Energies, 9(5), 349. (2016).
• 15
  Alba, S. A. & Manana, M. Energy Research in Airports: A Review. Energies, 9(5), 349. (2016).
• 16
  Ellerbeck, S. World Economic Forum, The aviation sector wants to reach net zero by 2050. How will it do it? https://www.weforum.org/agenda/2022/12/aviation-net-zero-emissions/ (2022).
• 17
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 18
  Ellerbeck, S. World Economic Forum, The aviation sector wants to reach net zero by 2050. How will it do it? https://www.weforum.org/agenda/2022/12/aviation-net-zero-emissions/ (2022).
• 19
  Ciliberti, D., Dellaa Vecchia, P., Memmolo, V., Nicolosi, F., Wortmann, G. & Ricci, F. The Enabling Technologies for a Quasi-Zero Emissions Commuter Aircraft. Aerospace, 9, 319. (2022).
• 20
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport  (2023).
• 21
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 22
  Colak, O., Enoch, M. & Morton, Craig. Airport business models and the COVID-19 pandemic: An exploration of the UK case study. Journal of Air Transport Management, Volume 108, 102337 (2023)
• 23
  European Union Aviation Safety Agency. European Aviation Environmental Report 2022 (2023).
• 24
  Greer, F., Rakas, J., Horvath, A. Airports and environmental sustainability: a comprehensive review. Environmental Research Letters, 15, 103007 (2020).
• 25
  Bergero, C., Gosnell, G., Gielen, D. et al. Pathways to net-zero emissions from aviation. Nature Sustainability 6, pp. 404–414 (2023).
• 26
  Hadded, F., Jagtap, S., Pagone, E. & Salonitis, K. Sustainability Assessment of Aerospace Manufacturing: An LCA-Based Framework. Global Conference on Sustainable Manufacturing, : Manufacturing Driving Circular Economy pp. 712-720 (2023)
• 27
  Harris, T., Landis, A. Space Sustainability Engineering: Quantitative Tools and Methods for Space Applications. 2019 IEEE Aerospace Conference (2019).
• 28
  Raj, A. & Srivastava, S. K. Sustainability performance assessment of an aircraft manufacturing firm. Benchmarking: An International Journal, 25(5), pp. 1500-1527. (2018).
• 29
  Petera, P., Wagner, J. Global Reporting Initiative (GRI) and its Reflections in the Literature. European Financial and Accounting Journal, Vol. 10, Iss. , pp. 13-32. (2015).
• 30
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 31
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 32
  Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).
• 33
  Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).
• 34
  Soundararajan, S. R., Vishnu, J., Manivasagam, G. & Muktinutalapati, N. R. Processing of beta titanium alloys for aerospace and biomedical applications. Titanium Alloys: Novel Aspects of Their Manufacturing and Processing. (2019).
• 35
  Nuss, P. & Eckelman, M. J. Life Cycle Assessment of Metals: A Scientific Synthesis. PLoS ONE 9(7): e101298 (2014)
• 36
  Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).
• 37
  Raj, A. & Srivastava, S. K. Sustainability performance assessment of an aircraft manufacturing firm. Benchmarking: An International Journal, 25(5), pp. 1500-1527. (2018).
• 38
  Xu, Y., Zhu, X., Wen, X. & Herrera-Viedma, E. Fuzzy best-worst method and its application in initial water rights allocation. Applied Soft Computing, Volume 101. (2021)
• 39
  Keivanpour, S. & Ait Kadi, D. End of life aircrafts recovery and green supply chain (a conceptual framework for addressing opportunities and challenges). Management Research Review, 38,10, pp. 1098-1124. (2015).
• 40
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 41
  The United State Environmental Protection Agency. Aerospace Manufacturing Sector–Pollution Prevention (P2) Opportunities. https://www.epa.gov/toxics-release-inventory-tri-program/aerospace-manufacturing-sector-pollution-prevention-p2 (2022).
• 42
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 43
  Statista. Verteilung der CO2-Emissionen weltweit nach Sektor bis 2021. https://de.statista.com/statistik/daten/studie/167957/umfrage/verteilung-der-co-emissionen-weltweit-nach-bereich/ (2022).
• 44
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 45
  Gössling, S. Why cities need to take road space from cars – and how this could be done. Journal of Urban Design, Volume 25, Issue 4 pp. 443-448. (2020).
• 46
  Statista. Anzahl der Flüge in der weltweiten Luftfahrt von 2014 bis 2022(in Millionen). https://de.statista.com/statistik/daten/studie/411620/umfrage/anzahl-der-weltweiten-fluege/ (2023).
• 47
  Statista. Statistiken zur weltweiten Luftfahrt. https://de.statista.com/themen/4313/weltweite-luftfahrt/#topicOverview (2023).
• 48
  Carroll, J., Brazil, W. Howard, M. & Denny, E. Imperfect emissions information during flight choices and the role of  CO2 labeling. Renewable and Sustainable Energy Reviews,  Volume 165, 112508. (2022).
• 49
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 50
  Samuels MPThe effects of flight and altitudeArchives of Disease in Childhood;89:448-455. (2004).
• 51
  Airbus. Composites: Airbus continues to shape the future. Airbus. https://www.airbus.com/en/newsroom/news/2017-08-composites-airbus-continues-to-shape-the-future (2017).
• 52
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022).
• 53
  Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).
• 54
  Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).
• 55
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022).
• 56
  ESA. Current landscape and future of SAF industry. ESA https://www.easa.europa.eu/eco/eaer/topics/sustainable-aviation-fuels/current-landscape-future-saf-industry (no date).
• 57
  MRAZOVA, Maria. Innovations, technology and efficiency shaping the aerospace environment P.92.
• 58
  Die Bundesregierung.  Nationale Wasserstoffstrategie, Energie aus klimafreundlichem Gas. Bundesregierung https://www.bundesregierung.de/breg-de/schwerpunkte/klimaschutz/wasserstoff-technologie-1732248#:~:text=Das%20Besondere%3A%20Dabei%20entstehen%20keine,Windkraftanlagen%20oder%20Solarmodulen%20erzeugt%20wird  (2023).
• 59
  Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).
• 60
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022).
• 61
  Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).
• 62
  bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).
• 63
  bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).
• 64
  Caset, f. Boussauw, k. & Storme, T. Meet & fly: Sustainable transport academics and the elephant in the room. Journal of Transport Geography, 70, 64-67 (2018).
• 65
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 4, (2022).
• 66
  bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).
• 67
  Wu, j, Gao, F, Li, S & Yang, F. Conceptual Design and Optimization of Distributed Electric Propulsion General Aviation Aircraft. Aerospace 10, 387 (2023).
• 68
  Airbus. Vahana: Our single-seat eVTOL demonstrator. Airbus. https://www.airbus.com/en/innovation/low-carbon-aviation/urban-air-mobility/cityairbus-nextgen/vahana  (No date).
• 69
  Joshi, G. How Is An Aircraft Refuelled? Refuelling an aircraft has its own process, and we take a look at how it’s done. Simple Flying. https://simpleflying.com/how-is-an-aircraft-refuled/ (2022).
• 70
  van Oosterom, S & Mitici, M. Optimizing the battery charging and swapping infrastructure for electric short-hauk aircraft – the case of electric flight in Norway. Transport Research Part C 155 (2023).
• 71
  Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022).
• 72
  Boeing. Boeing Reports Commercial Orders and Deliveries for 2022. Boeing. https://investors.boeing.com/investors/news/press-release-details/2023/Boeing-Reports-Commercial-Orders-and-Deliveries-for-2022/default.aspx (2023).
• 73
  Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).
• 74
  Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).
• 75
  Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022).
• 76
  Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022).
• 77
  Airbus. ZEROe: Towards the world’s first hydrogen-powered commercial aircraft. Airbus. https://www.airbus.com/en/innovation/low-carbon-aviation/hydrogen/zeroe (No date).
• 78
  Crifo, P., Escrig-Olmedo, E. & Mottis, N. Corporate governance as a key driver of corporate sustainability in France: the role of board members and investor relations. Journal of Business Ethics 159, 1127–1146 (2018).
• 79
  Zaman, R., Jain, T., Samara, G. & Jamali, D. Corporate governance meets corporate social responsibility: Mapping the interface. Business & Society 61, 690–752 (2020).
• 80
  Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).
• 81
  Gangi, F., Daniele, L. M. & Varrone, N. How do corporate environmental policy and corporate reputation affect risk‐adjusted financial performance? Business Strategy and the Environment 29, 1975–1991 (2020).
• 82
  Lockheed Martin. Board of Directors. Lockheed Martin https://www.lockheedmartin.com/en-us/who-we-are/leadership-governance/board-of-directors.html (2023).
• 83
  Boeing. Corporate Governance. Boeing https://www.boeing.com/company/general-info/corporate-governance.page (2023).
• 84
  General Electric. GE Board of Directors. GE Governance https://www.ge.com/investor-relations/governance (2023).
• 85
  Airbus. Board and Board Committees. Airbus https://www.airbus.com/en/our-governance/board-and-board-committees (2023).
• 86
  Khatib, S. F. A., Abdullah, D. F., Elamer, A. A. & Abueid, R. Nudging toward diversity in the boardroom: A systematic literature review of board diversity of financial institutions. Business Strategy and the Environment 30, 985–1002 (2020).
• 87
  Northrop Grumman. Company Leadership. Northrop Grumman https://www.northropgrumman.com/who-we-are/leadership (2023).
• 88
  Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).
• 89
  Lewis, A. & Loebbaka, J. Managing future and emergent strategy decay in the commercial aerospace industry. Business Strategy Series 9, 147–156 (2008).
• 90
  Lim, M., Luckert, M. K. & Qiu, F. Economic opportunities and challenges in biojet production: A literature review and analysis. Biomass & Bioenergy 170, 106727 (2023).
• 91
  Wu, P.-J. & Yang, C.-K. Sustainable development in aviation logistics: Successful drivers and business strategies. Business Strategy and the Environment 30, 3763–3771 (2021).
• 92
  Qiu, R., Hou, S., Chen, X. & Meng, Z. Green aviation industry sustainable development towards an integrated support system. Business Strategy and the Environment 30, 2441–2452 (2021).
• 93
  Scheelhaase, J., Maertens, S., Grimme, W. & Jung, M. H. EU ETS versus CORSIA – A critical assessment of two approaches to limit air transport’s CO 2 emissions by market-based measures. Journal of Air Transport Management 67, 55–62 (2018).
• 94
  Scheelhaase, J. & Maertens, S. How to improve the global ‘Carbon Offsetting and Reduction Scheme for International Aviation’ (CORSIA)? Transportation Research Procedia 51, 108–117 (2020).
• 95
  Mkono, M. Eco-anxiety and the flight shaming movement: implications for tourism. Journal of Tourism Futures 6, 223–226 (2020).
• 96
  Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).
• 97
  Safran Group. Corporate Officer Compensation (2021-2022). Safran Group https://www.safran-group.com/sites/default/files/2022-02/Corporate%20Officer%20Compensation%20%282021-2022%29.pdf (2022).
• 98
  Rolls-Royce. Director Remuneration Policy 2021. Rolls-Royce https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/annual-report/2021/director-remuneration-policy-2021.pdf (2021).
• 99
  Rolls-Royce. Annual Report 2021. Rolls-Royce https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/annual-report/2021/ar2021-strategic-report.pdf (2021).
• 100
  Lewis, A. & Loebbaka, J. Managing future and emergent strategy decay in the commercial aerospace industry. Business Strategy Series 9, 147–156 (2008).
• 101
  Gonzalez-Garay, A. et al. Unravelling the potential of sustainable aviation fuels to decarbonise the aviation sector. Energy and Environmental Science 15, 3291–3309 (2022).
• 102
  Scheelhaase, J. & Maertens, S. How to improve the global ‘Carbon Offsetting and Reduction Scheme for International Aviation’ (CORSIA)? Transportation Research Procedia 51, 108–117 (2020).
• 103
  Airbus. At Airbus, hydrogen power gathers pace. https://www.airbus.com/en/newsroom/stories/2023-06-at-airbus-hydrogen-power-gathers-pace (2023).
• 104
  Clancy, J. M., Gaffney, F., Deane, P., Curtis, J. & Gallachóir, B. P. Ó. Fossil fuel and CO2 emissions savings on a high renewable electricity system – A single year case study for Ireland. Energy Policy 83, 151–164 (2015).
• 105
  Airbus. Airbus’ most popular aircraft takes to the skies with 100% sustainable aviation fuel. https://www.airbus.com/en/newsroom/stories/2023-03-airbus-most-popular-aircraft-takes-to-the-skies-with-100-sustainable (2023).
• 106
  Tashie-Lewis, B. C. & Nnabuife, S. G. Hydrogen Production, Distribution, Storage and Power Conversion in a Hydrogen Economy – A Technology Review. Chemical Engineering Journal Advances 8, 100172 (2021).
• 107
  Lim, M., Luckert, M. K. & Qiu, F. Economic opportunities and challenges in biojet production: A literature review and analysis. Biomass & Bioenergy 170, 106727 (2023).
• 108
  McDonald, S., Oates, C., Thyne, M., Timmis, A. & Carlile, C. Flying in the face of environmental concern: why green consumers continue to fly. Journal of Marketing Management 31, 1503–1528 (2015).
• 109
  Schleiden, V. & Neiberger, C. Does sustainability matter? A structural equation model for cross-border online purchasing behaviour. The International Review of Retail, Distribution and Consumer Research 30, 46–67 (2019).
• 110
  Hansmann, R. & Binder, C. R. Reducing personal air-travel: Restrictions, options and the role of justifications. Transportation Research Part D-transport and Environment 96, 102859 (2021).
• 111
  Schmidt, F., Sidders, A., Czepkiewicz, M., Árnadóttir, Á. & Heinonen, J. ‘I am not a typical flyer’: narratives about the justified or excessive character of international flights in a highly mobile society. Journal of Sustainable Tourism 1–24 (2023).
• 112
  McDonald, S., Oates, C., Thyne, M., Timmis, A. & Carlile, C. Flying in the face of environmental concern: why green consumers continue to fly. Journal of Marketing Management 31, 1503–1528 (2015).

• 1
  United Nations. International Standard Industrial Classification of All Economic Activities ISIC Rev. 3.1. (2002).
• 2
  OECD. “Overview of the aerospace sector: background”, in The Space Economy at a Glance 2007 OECD Publishing, Paris. (2002).
• 3
  He, S., Hipel, K.W. & Kilgour, M. Analyzing market competition between Airbus and Boeing using a duo hierarchical graph model for conflict resolution. Journal of Systems Science and Systems Engineering, Volume 26, pages 683-710 (2017).
• 4
  Jones, M. Boeing vs. Airbus: The Key Reason Why Airbus Stock is Better https://www.nasdaq.com/articles/boeing-vs.-airbus:-the-key-reason-why-airbus-stock-is-better (2023).
• 5
  Statista. Umsatz der weltweit führenden Flugzeughersteller und Zulieferer im Jahr 2022(in Milliarden US-Dollar) https://de.statista.com/statistik/daten/studie/30808/umfrage/umsatz-der-weltweit-fuehrenden-flugzeughersteller/#:~:text=Airbus%20und%20Boeing%20sind%20die,vorn%2C%20was%20die%20Flugzeugauslieferungen%20anbelangt. (2023).
• 6
  Encyclopedia Britannica. Aviation https://www.britannica.com/technology/aviation (2023)
• 7
  Airbus. Non-Financial Information Annual Report (2021).
• 8
  Dias, V.M.R., Jugend, D., de Camargo Fiorini, P., do Amaral Razziono, C. Antonio Paula Pinhero, M. Possibilities for applying the circular economy in the aerospace industry: Practices, opportunities and challenges. Journal of Air Transport Management, Volume 102, 102227 (2022).
• 9
  Franchino, M. Framework for Sustainability in Aerospace: A Proof of Concept on Decision Making and Scenario Comparison. In: Kohl, H., Seliger, G., Dietrich, F. (eds) Manufacturing Driving Circular Economy. GCSM 2022. Lecture Notes in Mechanical Engineering. Springer, Cham. (2023).
• 10
  Abbasi, T., & Abbasi, S. A. Decarbonization of fossil fuels as a strategy to control global warming. Renewable and Sustainable Energy Reviews, 15(4), 1828. (2011).
• 11
  O. Yoro, K. & o. Dadmola, M. CO2 emission sources, greenhouse gases, and the global warming effect. Advances in Carbon Capture Methods, Technologies and Applications. pp. 3-28. (2020).
• 12
  Mishra, S. Is smog innocuous? Air pollution and cardiovascular disease. Indian Heart Journal, Volume 69, Issue 4, pp. 425-429. (2017).
• 13
  Greer, F., Rakas, J., Horvath, A. Airports and environmental sustainability: a comprehensive review. Environmental Research Letters, 15, 103007 (2020).
• 14
  Alba, S. A. & Manana, M. Energy Research in Airports: A Review. Energies, 9(5), 349. (2016).
• 15
  Alba, S. A. & Manana, M. Energy Research in Airports: A Review. Energies, 9(5), 349. (2016).
• 16
  Ellerbeck, S. World Economic Forum, The aviation sector wants to reach net zero by 2050. How will it do it? https://www.weforum.org/agenda/2022/12/aviation-net-zero-emissions/ (2022).
• 17
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 18
  Ellerbeck, S. World Economic Forum, The aviation sector wants to reach net zero by 2050. How will it do it? https://www.weforum.org/agenda/2022/12/aviation-net-zero-emissions/ (2022).
• 19
  Ciliberti, D., Dellaa Vecchia, P., Memmolo, V., Nicolosi, F., Wortmann, G. & Ricci, F. The Enabling Technologies for a Quasi-Zero Emissions Commuter Aircraft. Aerospace, 9, 319. (2022).
• 20
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport  (2023).
• 21
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 22
  Colak, O., Enoch, M. & Morton, Craig. Airport business models and the COVID-19 pandemic: An exploration of the UK case study. Journal of Air Transport Management, Volume 108, 102337 (2023)
• 23
  European Union Aviation Safety Agency. European Aviation Environmental Report 2022 (2023).
• 24
  Greer, F., Rakas, J., Horvath, A. Airports and environmental sustainability: a comprehensive review. Environmental Research Letters, 15, 103007 (2020).
• 25
  Bergero, C., Gosnell, G., Gielen, D. et al. Pathways to net-zero emissions from aviation. Nature Sustainability 6, pp. 404–414 (2023).
• 26
  Hadded, F., Jagtap, S., Pagone, E. & Salonitis, K. Sustainability Assessment of Aerospace Manufacturing: An LCA-Based Framework. Global Conference on Sustainable Manufacturing, : Manufacturing Driving Circular Economy pp. 712-720 (2023)
• 27
  Harris, T., Landis, A. Space Sustainability Engineering: Quantitative Tools and Methods for Space Applications. 2019 IEEE Aerospace Conference (2019).
• 28
  Raj, A. & Srivastava, S. K. Sustainability performance assessment of an aircraft manufacturing firm. Benchmarking: An International Journal, 25(5), pp. 1500-1527. (2018).
• 29
  Petera, P., Wagner, J. Global Reporting Initiative (GRI) and its Reflections in the Literature. European Financial and Accounting Journal, Vol. 10, Iss. , pp. 13-32. (2015).
• 30
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 31
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 32
  Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).
• 33
  Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).
• 34
  Soundararajan, S. R., Vishnu, J., Manivasagam, G. & Muktinutalapati, N. R. Processing of beta titanium alloys for aerospace and biomedical applications. Titanium Alloys: Novel Aspects of Their Manufacturing and Processing. (2019).
• 35
  Nuss, P. & Eckelman, M. J. Life Cycle Assessment of Metals: A Scientific Synthesis. PLoS ONE 9(7): e101298 (2014)
• 36
  Dolganova, I., Bach, V., Rödl, A., Kaltschmitt, M. & Finkbeiner, M. Assessment of Critical Resource Use in Aircraft Manufacturing. Circular Economy and Sustainability. 2, pp. 1193–1212 (2022).
• 37
  Raj, A. & Srivastava, S. K. Sustainability performance assessment of an aircraft manufacturing firm. Benchmarking: An International Journal, 25(5), pp. 1500-1527. (2018).
• 38
  Xu, Y., Zhu, X., Wen, X. & Herrera-Viedma, E. Fuzzy best-worst method and its application in initial water rights allocation. Applied Soft Computing, Volume 101. (2021)
• 39
  Keivanpour, S. & Ait Kadi, D. End of life aircrafts recovery and green supply chain (a conceptual framework for addressing opportunities and challenges). Management Research Review, 38,10, pp. 1098-1124. (2015).
• 40
  Modarress Fathi, B., Ansari, A., Ansari. A. Green Commercial Aviation Supply Chain—A European Path to Environmental Sustainability. Sustainability, Volume 15, 6574 (2023).
• 41
  The United State Environmental Protection Agency. Aerospace Manufacturing Sector–Pollution Prevention (P2) Opportunities. https://www.epa.gov/toxics-release-inventory-tri-program/aerospace-manufacturing-sector-pollution-prevention-p2 (2022).
• 42
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 43
  Statista. Verteilung der CO2-Emissionen weltweit nach Sektor bis 2021. https://de.statista.com/statistik/daten/studie/167957/umfrage/verteilung-der-co-emissionen-weltweit-nach-bereich/ (2022).
• 44
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 45
  Gössling, S. Why cities need to take road space from cars – and how this could be done. Journal of Urban Design, Volume 25, Issue 4 pp. 443-448. (2020).
• 46
  Statista. Anzahl der Flüge in der weltweiten Luftfahrt von 2014 bis 2022(in Millionen). https://de.statista.com/statistik/daten/studie/411620/umfrage/anzahl-der-weltweiten-fluege/ (2023).
• 47
  Statista. Statistiken zur weltweiten Luftfahrt. https://de.statista.com/themen/4313/weltweite-luftfahrt/#topicOverview (2023).
• 48
  Carroll, J., Brazil, W. Howard, M. & Denny, E. Imperfect emissions information during flight choices and the role of  CO2 labeling. Renewable and Sustainable Energy Reviews,  Volume 165, 112508. (2022).
• 49
  International Energy Agency. Energy- system Transport. https://www.iea.org/energy-system/transport (2023).
• 50
  Samuels MPThe effects of flight and altitudeArchives of Disease in Childhood;89:448-455. (2004).
• 51
  Airbus. Composites: Airbus continues to shape the future. Airbus. https://www.airbus.com/en/newsroom/news/2017-08-composites-airbus-continues-to-shape-the-future (2017).
• 52
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022).
• 53
  Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).
• 54
  Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).
• 55
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022).
• 56
  ESA. Current landscape and future of SAF industry. ESA https://www.easa.europa.eu/eco/eaer/topics/sustainable-aviation-fuels/current-landscape-future-saf-industry (no date).
• 57
  MRAZOVA, Maria. Innovations, technology and efficiency shaping the aerospace environment P.92.
• 58
  Die Bundesregierung.  Nationale Wasserstoffstrategie, Energie aus klimafreundlichem Gas. Bundesregierung https://www.bundesregierung.de/breg-de/schwerpunkte/klimaschutz/wasserstoff-technologie-1732248#:~:text=Das%20Besondere%3A%20Dabei%20entstehen%20keine,Windkraftanlagen%20oder%20Solarmodulen%20erzeugt%20wird  (2023).
• 59
  Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).
• 60
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 15, (2022).
• 61
  Bauen, Ausilio et al. Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnsons Matthey Technol. Rev. 64, 263-278 (2020).
• 62
  bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).
• 63
  bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).
• 64
  Caset, f. Boussauw, k. & Storme, T. Meet & fly: Sustainable transport academics and the elephant in the room. Journal of Transport Geography, 70, 64-67 (2018).
• 65
  Cabrera, Eduardo & M. Melo de Sousa, Joao. J.M.M. Use of Sustainable Fuels in Aviation – A Review. Energies 4, (2022).
• 66
  bright Appiah, Adu-Gyamfi & Good, Clara. Electric aviation: A review of concepts and enabling technologies. Transportation Engineering 9, 9 (2022).
• 67
  Wu, j, Gao, F, Li, S & Yang, F. Conceptual Design and Optimization of Distributed Electric Propulsion General Aviation Aircraft. Aerospace 10, 387 (2023).
• 68
  Airbus. Vahana: Our single-seat eVTOL demonstrator. Airbus. https://www.airbus.com/en/innovation/low-carbon-aviation/urban-air-mobility/cityairbus-nextgen/vahana  (No date).
• 69
  Joshi, G. How Is An Aircraft Refuelled? Refuelling an aircraft has its own process, and we take a look at how it’s done. Simple Flying. https://simpleflying.com/how-is-an-aircraft-refuled/ (2022).
• 70
  van Oosterom, S & Mitici, M. Optimizing the battery charging and swapping infrastructure for electric short-hauk aircraft – the case of electric flight in Norway. Transport Research Part C 155 (2023).
• 71
  Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022).
• 72
  Boeing. Boeing Reports Commercial Orders and Deliveries for 2022. Boeing. https://investors.boeing.com/investors/news/press-release-details/2023/Boeing-Reports-Commercial-Orders-and-Deliveries-for-2022/default.aspx (2023).
• 73
  Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).
• 74
  Boeing. Sustainability Report: Sustainable Aerospace Together. (2022).
• 75
  Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022).
• 76
  Airbus. Airbus Annual Report 2022: Progressing with purpose. (2022).
• 77
  Airbus. ZEROe: Towards the world’s first hydrogen-powered commercial aircraft. Airbus. https://www.airbus.com/en/innovation/low-carbon-aviation/hydrogen/zeroe (No date).
• 78
  Crifo, P., Escrig-Olmedo, E. & Mottis, N. Corporate governance as a key driver of corporate sustainability in France: the role of board members and investor relations. Journal of Business Ethics 159, 1127–1146 (2018).
• 79
  Zaman, R., Jain, T., Samara, G. & Jamali, D. Corporate governance meets corporate social responsibility: Mapping the interface. Business & Society 61, 690–752 (2020).
• 80
  Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).
• 81
  Gangi, F., Daniele, L. M. & Varrone, N. How do corporate environmental policy and corporate reputation affect risk‐adjusted financial performance? Business Strategy and the Environment 29, 1975–1991 (2020).
• 82
  Lockheed Martin. Board of Directors. Lockheed Martin https://www.lockheedmartin.com/en-us/who-we-are/leadership-governance/board-of-directors.html (2023).
• 83
  Boeing. Corporate Governance. Boeing https://www.boeing.com/company/general-info/corporate-governance.page (2023).
• 84
  General Electric. GE Board of Directors. GE Governance https://www.ge.com/investor-relations/governance (2023).
• 85
  Airbus. Board and Board Committees. Airbus https://www.airbus.com/en/our-governance/board-and-board-committees (2023).
• 86
  Khatib, S. F. A., Abdullah, D. F., Elamer, A. A. & Abueid, R. Nudging toward diversity in the boardroom: A systematic literature review of board diversity of financial institutions. Business Strategy and the Environment 30, 985–1002 (2020).
• 87
  Northrop Grumman. Company Leadership. Northrop Grumman https://www.northropgrumman.com/who-we-are/leadership (2023).
• 88
  Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).
• 89
  Lewis, A. & Loebbaka, J. Managing future and emergent strategy decay in the commercial aerospace industry. Business Strategy Series 9, 147–156 (2008).
• 90
  Lim, M., Luckert, M. K. & Qiu, F. Economic opportunities and challenges in biojet production: A literature review and analysis. Biomass & Bioenergy 170, 106727 (2023).
• 91
  Wu, P.-J. & Yang, C.-K. Sustainable development in aviation logistics: Successful drivers and business strategies. Business Strategy and the Environment 30, 3763–3771 (2021).
• 92
  Qiu, R., Hou, S., Chen, X. & Meng, Z. Green aviation industry sustainable development towards an integrated support system. Business Strategy and the Environment 30, 2441–2452 (2021).
• 93
  Scheelhaase, J., Maertens, S., Grimme, W. & Jung, M. H. EU ETS versus CORSIA – A critical assessment of two approaches to limit air transport’s CO 2 emissions by market-based measures. Journal of Air Transport Management 67, 55–62 (2018).
• 94
  Scheelhaase, J. & Maertens, S. How to improve the global ‘Carbon Offsetting and Reduction Scheme for International Aviation’ (CORSIA)? Transportation Research Procedia 51, 108–117 (2020).
• 95
  Mkono, M. Eco-anxiety and the flight shaming movement: implications for tourism. Journal of Tourism Futures 6, 223–226 (2020).
• 96
  Gangi, F., Mustilli, M., Daniele, L. M. & Coscia, M. The sustainable development of the aerospace industry: Drivers and impact of corporate environmental responsibility. Business Strategy and the Environment 31, 218–235 (2021).
• 97
  Safran Group. Corporate Officer Compensation (2021-2022). Safran Group https://www.safran-group.com/sites/default/files/2022-02/Corporate%20Officer%20Compensation%20%282021-2022%29.pdf (2022).
• 98
  Rolls-Royce. Director Remuneration Policy 2021. Rolls-Royce https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/annual-report/2021/director-remuneration-policy-2021.pdf (2021).
• 99
  Rolls-Royce. Annual Report 2021. Rolls-Royce https://www.rolls-royce.com/~/media/Files/R/Rolls-Royce/documents/annual-report/2021/ar2021-strategic-report.pdf (2021).
• 100
  Lewis, A. & Loebbaka, J. Managing future and emergent strategy decay in the commercial aerospace industry. Business Strategy Series 9, 147–156 (2008).
• 101
  Gonzalez-Garay, A. et al. Unravelling the potential of sustainable aviation fuels to decarbonise the aviation sector. Energy and Environmental Science 15, 3291–3309 (2022).
• 102
  Scheelhaase, J. & Maertens, S. How to improve the global ‘Carbon Offsetting and Reduction Scheme for International Aviation’ (CORSIA)? Transportation Research Procedia 51, 108–117 (2020).
• 103
  Airbus. At Airbus, hydrogen power gathers pace. https://www.airbus.com/en/newsroom/stories/2023-06-at-airbus-hydrogen-power-gathers-pace (2023).
• 104
  Clancy, J. M., Gaffney, F., Deane, P., Curtis, J. & Gallachóir, B. P. Ó. Fossil fuel and CO2 emissions savings on a high renewable electricity system – A single year case study for Ireland. Energy Policy 83, 151–164 (2015).
• 105
  Airbus. Airbus’ most popular aircraft takes to the skies with 100% sustainable aviation fuel. https://www.airbus.com/en/newsroom/stories/2023-03-airbus-most-popular-aircraft-takes-to-the-skies-with-100-sustainable (2023).
• 106
  Tashie-Lewis, B. C. & Nnabuife, S. G. Hydrogen Production, Distribution, Storage and Power Conversion in a Hydrogen Economy – A Technology Review. Chemical Engineering Journal Advances 8, 100172 (2021).
• 107
  Lim, M., Luckert, M. K. & Qiu, F. Economic opportunities and challenges in biojet production: A literature review and analysis. Biomass & Bioenergy 170, 106727 (2023).
• 108
  McDonald, S., Oates, C., Thyne, M., Timmis, A. & Carlile, C. Flying in the face of environmental concern: why green consumers continue to fly. Journal of Marketing Management 31, 1503–1528 (2015).
• 109
  Schleiden, V. & Neiberger, C. Does sustainability matter? A structural equation model for cross-border online purchasing behaviour. The International Review of Retail, Distribution and Consumer Research 30, 46–67 (2019).
• 110
  Hansmann, R. & Binder, C. R. Reducing personal air-travel: Restrictions, options and the role of justifications. Transportation Research Part D-transport and Environment 96, 102859 (2021).
• 111
  Schmidt, F., Sidders, A., Czepkiewicz, M., Árnadóttir, Á. & Heinonen, J. ‘I am not a typical flyer’: narratives about the justified or excessive character of international flights in a highly mobile society. Journal of Sustainable Tourism 1–24 (2023).
• 112
  McDonald, S., Oates, C., Thyne, M., Timmis, A. & Carlile, C. Flying in the face of environmental concern: why green consumers continue to fly. Journal of Marketing Management 31, 1503–1528 (2015).