How significant a source of emissions is air travel?

Aircraft are a rapidly growing emissions source within the transportation sector, which has surpassed the power sector as the biggest source of U.S. carbon dioxide emissions. In 2018, aircraft were responsible for about 3 percent of total U.S. carbon dioxide emissions and nearly 9 percent of greenhouse gas emissions from the U.S. transportation sector. Commercial air travel accounted for most of the aircraft carbon dioxide emissions, with military and general aviation making up the rest.

From 1990 to 2018, U.S. carbon dioxide emissions from domestic commercial flights grew about 18 percent. Recent studies estimate that U.S. aircraft emissions will increase substantially in the next 20 years. Moreover, airplanes remain the single largest source of carbon dioxide emissions within the U.S. transportation sector that is not yet subject to federal greenhouse gas regulations.

U.S. aviation is part of the increasingly interconnected global aviation sector, which makes up more than 2 percent of global carbon dioxide emissions but is one of the fastest growing sources. From 1990 to 2010, global aircraft carbon dioxide emissions grew about 40 percent. From 2013 to 2018, global emissions grew another 26 percent. If global aviation were a country, it would rank as the 20th largest carbon dioxide emitter, and U.S. aircraft emissions are 24 percent of all global aircraft emissions. Absent new policies, global aircraft emissions are projected to triple by 2050.

Global action to address aircraft emissions

Unlike stationary sources, such as power plants, and many mobile sources, such as cars, aircraft frequently travel between jurisdictions with different environmental laws and standards. As such, the United Nations’ International Civil Aviation Organization (ICAO) serves as a global forum to develop policies and standards for the global industry, including a comprehensive set of measures to address greenhouse gas emissions.

In 2010, the aviation industry’s goal of carbon neutral growth from 2020 onwards was formally adopted by ICAO. Within the sector, the key pathways to reduce emissions are improvements in aircraft technology, improvements in operations and infrastructure, and further use of aviation biofuels.

At the 39th ICAO Assembly in October 2016, member states agreed to policies to meet the carbon-neutral goal, international carbon dioxide standards for aircraft, and a market-based mechanism to offset aviation emissions with reductions in other sectors.

Traditionally, both the U.S. Environmental Protection Agency (EPA) and the Federal Aviation Administration (FAA) have worked within the ICAO process to establish international emission standards and related requirements for other pollutants. Under this approach, international emission standards are first adopted by ICAO, and EPA subsequently initiates rulemaking under section 231 of the Clean Air Act to establish domestic standards equivalent to international standards where appropriate.

What is the status of U.S. regulation?

A 2016 final endangerment finding determined that greenhouse gas emissions from aircraft contribute to air pollution that could endanger public health and welfare, requiring the EPA to monitor and regulate greenhouse gas emissions from aircraft under the Clean Air Act.

In December 2020, EPA finalized greenhouse gas standards for aircraft, requiring aircraft manufacturers to meet fuel efficient limits based on its specific aircraft/engine combination and size of fuselage. The final rule would have the same emissions limit as the ICAO carbon dioxide emission standards. Basing these standards on the internationally accepted standards allows U.S. aircraft to continue to be used around the world.

Covered aircraft include subsonic jet aircraft — ranging from smaller jet aircraft such as the Cessna Citation CJ3+ to larger jet aircraft such as the Boeing 777 — and subsonic turboprop aircraft — such as the Viking Q400. The rule would apply to new aircraft designs submitted to the FAA for certification starting in 2023, and to aircraft in production starting in 2028.