Aircraft engines produce gases, noise, and particulates from fossil fuel combustion, raising environmental concerns over both global impacts and their effects on local air quality.Jet airliners contribute to climate change by emitting carbon dioxide (CO2), the best understood greenhouse gas, and, with less scientific understanding, nitrogen oxides, contrails and particulates.Their radiative forcing is estimated at 1.3–1.4 that of CO2 alone, excluding induced cirrus cloud which remains poorly understood scientifically.In 2018, global commercial operations generated 2.4% of all CO2 emissions.
Jet airliners became about 70% more fuel efficient between 1967 and 2007, and CO2 emissions per revenue ton-kilometer (RTK) in 2018 were 47% of those in 1990. In 2018, CO2 emissions averaged 88 grams of CO2 per revenue passenger per km.While the aviation industry is more fuel efficient, overall emissions have risen as the volume of air travel has increased. By 2020, aviation emissions were 70% higher than in 2005 and they could grow by 300% by 2050.