The U.S. Environmental Protection Agency (EPA) will propose greenhouse gas standards for aircraft after the agency concluded those emissions endanger human health and the environment.

The July 25, 2016 finding, issued under Section 231(a) of the Clean Air Act, triggers a requirement for the EPA to set emissions limits for the aircraft. The EPA declined to say when a proposed rule would be issued. It did say, however, that future regulatory efforts are likely to be at least as strict as those expected to be approved by the International Civil Aviation Organization in March 2017.

So-called "covered aircraft" include the A-380 and Boeing 747.So-called "covered aircraft" include the A-380 and Boeing 747.The endangerment finding concludes that carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulfur hexafluoride from certain aircraft engines contribute to climate change. It does not apply to small piston-engine planes or to military aircraft.

According to EPA, 89% of U.S. aircraft emissions are covered under the EPA's finding. U.S. aircraft generate 3% of total domestic greenhouse gas emissions and account for 29% of global emissions from the sector.

The contribution finding concludes that GHG emissions from certain classes of engines used in “U.S. covered aircraft” contribute to the air pollution that endangers public health and welfare.

The EPA defines “U.S. covered aircraft” to be subsonic jet aircraft with a maximum takeoff mass (MTOM) greater than 5,700 kilograms and subsonic propeller driven aircraft, (for example, turboprops) with a MTOM greater than 8,618 kilograms.

Examples of covered aircraft include smaller jet aircraft such as the Cessna Citation CJ3+ and the Embraer E170, up to the largest commercial jet aircraft, the Airbus A380 and the Boeing 747. Examples of covered turboprop aircraft include larger turboprop aircraft, such as the ATR 72 and the Bombardier Q400. The scope of covered aircraft aligns with the applicability thresholds (based on MTOM) for the international aircraft CO2 standard, EPA says.

The EPA stopped short at this time in making a contribution finding for GHG emissions from engines not used in covered aircraft (for example, those used in smaller turboprops, smaller jet aircraft, piston-engine aircraft, helicopters and military aircraft). Examples of aircraft that are not covered include smaller turboprop aircraft, such as the Beechcraft King Air 350i, and smaller jet aircraft, such as the Cessna Citation M2.

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