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Contrails are line-shaped clouds or “Condensation trails” composed of ice particles that are visible behind jet aircraft engines under certain atmospheric conditions and at times can persist. EPA is not aware of any deliberate actions to release chemical or biological agents into the atmosphere. If you have a question, please email us at (or call the contrail information line at 734-214-4432 to hear this message).

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This page provides information about air pollutant emissions from aviation. It includes regulations, guidance, and other information related to aircraft.

EPA Finalizes Clean Air Act Finding that Greenhouse Gas Emissions from Certain Classes of Aircraft Endanger Human Health and Welfare

The EPA finalized findings that greenhouse gas (GHG) emissions from certain classes of engines used in aircraft contribute to the air pollution that causes climate change endangering public health and welfare under section 231(a) of the Clean Air Act. These findings focus on the six well-mixed GHGs that together represent the largest driver of human-caused climate change: carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. The EPA’s final endangerment and contribution findings for aircraft GHG emissions are in preparation for a future domestic rulemaking process to adopt future GHG standards. Any future proposed aircraft engine standards would also be open to public comment and review before they could take effect.

EPA Takes First Steps to Address Greenhouse Gas Emissions from Aircraft

The EPA proposed to find that greenhouse gas (GHG) emissions from certain classes of engines used in aircraft contribute to the air pollution that causes climate change endangering public health and welfare under section 231(a) of the Clean Air Act. At the same time, EPA issued an Advance Notice of Proposed Rulemaking that provides information on the process for setting international CO2 emissions standards for aircraft at the International Civil Aviation Organization, and describes and seeks input on issues related to setting an international CO2 standard for aircraft, and the potential use of section 231 of the Clean Air Act to adopt a corresponding aircraft engine standard domestically.

EPA Notifies ICAO of Timeframe for Initiating U.S. Domestic Process to Address Aircraft GHGs

The United States recently submitted an information paper to the United Nation’s International Civil Aviation Organization (ICAO) that sets out a timeframe for initiating the U.S. domestic regulatory process for addressing greenhouse gas emissions from aircraft under the Clean Air Act.

NOx Emissions from Commercial Aircraft Engines

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Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline

The EPA is evaluating the impact of lead emissions from aircraft using leaded aviation gasoline in order to make a determination regarding whether aircraft lead emissions cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. These actions are in response to petitioners’ requests, which are provided below along with the EPA responses to date. The EPA currently intends to issue a proposed finding on the question of endangerment in 2017. This proposed finding will then undergo public notice and comment. After evaluating comments on the proposal, we plan to issue a final endangerment finding in 2018. Documents and information relevant to the EPA’s ongoing evaluation and other EPA activities regarding lead in air are provided below.

In separate activities related to the National Ambient Air Quality Standards for lead, EPA finalized revisions to the ambient monitoring requirements for measuring lead in the air on December 14, 2010. These amendments expanded the nation's lead monitoring network to better assess compliance with the 2008 National Ambient Air Quality Standards for lead. EPA required the continuation of monitoring at airports emitting at least one ton of lead per year. EPA also required the states to conduct a year-long monitoring study at 15 airports that emit less than one ton per year to determine how these sources impact air quality.

The following documents provide information on inventory documentation and additional data:

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