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.

Aircraft noise pollution disrupts sleep, children's education and could increase cardiovascular risk. Airports can generate water pollution due to their extensive handling of jet fuel and deicing chemicals if not contained, contaminating nearby water bodies. Aviation activities emit ozone and ultrafine particles, both of which are health hazards. Piston engines used in general aviation burn Avgas, releasing toxic lead.

Aviation's environmental footprint can be reduced by better fuel economy in aircraft, or air traffic control and flight routes can be optimized to lower non-CO₂ effects on climate from NO
_x, particulates or contrails. Aviation biofuel, emissions trading and carbon offsetting, part of the ICAO's CORSIA, can lower CO₂ emissions. Aviation usage can be lowered by short-haul flight bans, train connections, personal choices and aviation taxation and subsidies. Fuel-powered aircraft may be replaced by hybrid electric aircraft and electric aircraft or by hydrogen-powered aircraft. Since 2021, the IATA members plan net-zero carbon emissions by 2050, followed by the ICAO in 2022.

Airplanes emit gases (carbon dioxide, water vapor, nitrogen oxides or carbon monoxide − bonding with oxygen to become CO₂ upon release) and atmospheric particulates (incompletely burned hydrocarbons, sulfur oxides, black carbon), interacting among themselves and with the atmosphere. While the main greenhouse gas emission from powered aircraft is CO₂, jet airliners contribute to climate change in four ways as they fly in the tropopause:

In 1999, the IPCC estimated aviation's radiative forcing in 1992 to be 2.7 (2 to 4) times that of CO₂ alone − excluding the potential effect of cirrus cloud enhancement. This was updated for 2000, with aviation's radiative forcing estimated at 47.8 mW/m², 1.9 times the effect of CO₂ emissions alone, 25.3 mW/m².

In 2005, research by David S. Lee, et al., published in the scientific journal Atmospheric Environment estimated the cumulative radiative forcing effect of aviation as 55 mW/m², which is twice the 28 mW/m² radiative forcing effect of the cumulative CO₂ emissions alone, excluding induced cirrus clouds. In 2012, research from Chalmers university estimated this weighting factor at 1.3–1.4 if aviation induced cirrus is not included, 1.7–1.8 if they are included (within a range of 1.3–2.9). This ratio depends on how aviation activity grows. If the growth is exponential then the ratio is constant. But if the growth stops, the ratio will go down because the CO₂ in the atmosphere due to aviation will continue to go up, whereas the other effects will stagnate.

Uncertainties remain on the NO_x–O₃–CH₄ interactions, aviation-produced contrails formation, the effects of soot aerosols on cirrus clouds and measuring non-CO₂ radiative forcing.