Sustainable Aviation 101

• The commercial aviation industry, currently responsible for approximately 3.5 percent of global climate change, is rapidly expanding.
• High costs are a major barrier to reducing the environmental impact of the aviation industry. However, policy options that encourage the development of sustainable aviation fuels and technologies, as well as more sustainable consumer behaviors, can help lessen the sector’s environmental impact cost-effectively.
• Policies that discourage fossil fuel consumption and frequent flying can complement incentives to invest in sustainable aviation.
• More research is needed to understand how consumers, costs, and the environment will be affected by efforts to make the aviation sector less harmful to human health and the climate.

Commercial aviation is responsible for approximately 3.5 percent of global climate change. Carbon emissions from aviation have doubled since the mid-1980s and could use up a quarter of the global carbon budget to limit warming to 1.5°C by 2050. Finding ways to make aviation more sustainable will be critical to improving human health and environmental outcomes.

But doing so will be difficult. Low-emission aviation fuels and technologies are expensive and in the early stages of development. For international flights, it is difficult to determine who bears responsibility for the environmental impacts from international emissions, as well as who is responsible for finding solutions.

However, several countries, airlines, and international aviation organizations have begun developing ambitious sustainability plans. Because individual airplanes have lifespans of up to 30 years, today’s innovations can make big contributions to medium- and long-term climate goals.

This explainer details key challenges to reducing aviation’s environmental impact and outlines potential technology and policy options for overcoming these challenges.

The aviation industry is proactively pursuing fuel efficiency through innovations in technology and operational methods. Despite notable improvements in per-passenger emissions, aviation’s overall emissions are increasing as more people take to the skies. Solutions to reduce environmental impacts will not only have to be cost-effective, but they will also have to outpace the sector’s growing environmental impact.

Sustainable aviation fuel (SAF), which is produced from fats, sugars, and other raw materials, offers an immediate, viable alternative to traditional jet fuel as it is compatible with existing aircraft. These raw materials (called "feedstocks") are transformed into SAF through various technological pathways. However, the production of feedstocks is costly and far below global demand. Other industries, such as long-haul trucking, are also vying for a share of available feedstocks for use in their own sustainable fuels.

Different types of feedstock and pathways face specific challenges. A significant portion of feedstock comes from agricultural products (such as corn) and ramping up production unsustainably could contribute to deforestation, food insecurity, and habitat destruction. Feedstock produced from industry byproducts, wastes, and residues, on the other hand, is scarce and hard to produce at scale. A universal challenge across the spectrum of feedstocks and pathways is the burden of high production costs, amplified by a general lack of financial backing resulting from the considerable market risks tied to funding innovative technologies.

Alternatives to sustainable aviation fuel, such as hydrogen fuel and—to a lesser extent—electrification, could also help reduce the environmental and health impacts of aviation in the longer term. Hybrid-electric aircraft, which utilize multiple energy sources to decrease fuel consumption, offer an additional pathway.

However, hydrogen, electric, and hybrid aircraft are emerging technologies that cannot yet carry as many passengers or travel as far as conventional ones, and their environmental benefits depend on how the fuel is produced. Safety concerns and public perceptions of safety also abound. Overcoming these challenges would require major changes to airports and nothing short of a technological revolution to develop and build these aircraft. Doing so would require new research, financial investments, operation systems, partnerships, and more to pull off—costly endeavors to undertake while airlines work to maintain customer satisfaction and business interests.

Airline passenger behavior is another challenge to overcome. Aviation demand and emissions have been rapidly growing over the past few decades. Encouraging people to take less carbon-intensive modes of transportation would reduce demand for aviation, and, by extension, contribute to a reduction in aviation emissions. Changing passenger behavior would require other modes of transportation, like rail, to improve infrastructure and offer competitive pricing and a better customer experience than airlines.

There is also a big-picture question of who is responsible for aviation emissions. Many flights are international and generate emissions across multiple countries and into international airspace, raising existential questions over which nation (or nations) should be responsible for a flight’s emissions. Both the Kyoto Protocol—a landmark climate agreement signed by over 80 countries in 1994—and the Paris Agreement—signed in 2016—do not explicitly require nations to include international aviation emissions in their climate goals. Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), introduced by the International Civil Aviation Organization in 2016, aims to manage these international emissions by placing the onus on airlines, not nations.

Truly lowering emissions requires more than just airlines stepping up; it requires the collective action of multiple stakeholders. Coordinated efforts highlight the importance of nations taking charge and crafting policies that address international aviation emissions. Resolving this issue will be important but will require significant international cooperation and debate.

Many policy options target the high costs associated with sustainable fuels and technologies. Tax credits and grants in the United States, for example, are being used to help the private sector reduce the high costs associated with researching, producing, and building sustainable fuels, infrastructure, and airports. Government-led research, for example at the US Department of Energy, is also a direct way to fund high-cost initiatives to reduce costs and improve efficiency.

Governments can also institute mandates and standards. To encourage the use of sustainable aviation fuel, which is currently one of the most practical solutions, governments can pass mandates that require a certain percentage of sustainable aviation fuel to be blended with traditional fuels. In 2023, the EU set a precedent by enacting the ReFuelEU Aviation initiative—the world's largest SAF mandate. Tighter emissions standards, too, can limit the amount of greenhouse gases that aircraft can emit, which encourages companies to seek out more sustainable options to comply with the regulations.

Other policy options can increase the costs of using fossil fuels. Market-based measures, such as carbon pricing, emissions trading systems, fossil fuel taxes, and carbon offset requirements create financial motivations for airlines to reduce their environmental footprints and adopt sustainable fuel and technology alternatives. However, there are concerns that these types of policies could increase prices for consumers.

Policies that focus on reducing overall fuel demand can also be effective. Government policies can encourage customers to make more sustainable travel choices, such as flying less, using ground transportation for domestic travel, choosing less carbon-intensive flights, and investing in reputable carbon offsets. Changes to corporate travel policies, too, may be necessary. For example, there are growing discussions around “frequent flyer taxes,” which could levy a tax on flights taken by individuals who fly several times in one year.

In recognition of the significant impact of international flights on global aviation emissions, there is a growing consensus on the need for international cooperation alongside national policies. The International Civil Aviation Organization’s adoption of CORSIA is a highly relevant example. Some options to address the problem’s global scale include attributing emissions to the country where the fuel was sold or to the country in which the emitting aircraft departed. However, attributing aviation emissions to individual countries is a complex issue and will require further international cooperation.

Making aviation more sustainable is a new frontier in combatting climate change. Researchers and policymakers are still learning about how consumers, costs, and the environment will be affected by efforts to make the aviation sector less harmful to human health and the climate. More research and policy evaluation will be necessary to effectively implement policies and practices that will overcome the challenges associated with bringing sustainable alternatives to scale.