On July 25, 2016 the United States Environmental Protection Agency (EPA) issued a finding that aircraft emissions of six greenhouse gases (GHGs), including carbon dioxide, are endangering public health and welfare by contributing to climate change (the Endangerment Finding). The Endangerment Finding does not initiate any immediate regulation of aircraft GHG emissions, but is the first step necessary in for EPA to promulgate such regulations.

According to EPA, aircraft are the “largest GHG-emitting transportation source not yet subject to GHG standards in the US,” and are responsible for 12 percent of transportation emissions in the US and three percent of total GHG emissions in the US. The Endangerment Finding covers approximately 90 percent of US aircraft, ranging from small private jets and propeller-driven craft such as Cessna models to the largest commercial jets like the Boeing 747. The smallest jet and propeller-driven aircraft, helicopters, and military aircraft are not covered.

The Endangerment Finding was issued under Section 231(a) of the Clean Air Act (CAA), which requires EPA to develop emissions standards for aircraft if it determines that those emissions endanger public health and welfare. These emissions standards will reflect scientific understanding of aircraft contribution to climate change; global standards set by the International Civil Aviation Organization; and technological feasibility. EPA and the Federal Aviation Administration will then coordinate the effort to enforce the new standards. This activity is parallel to the process required by CAA Section 202(a), under which EPA issued an endangerment finding for motor vehicle GHG emissions in 2009 and subsequently developed emissions standards that have been implemented and enforced in concert with the National Highway Traffic Safety Administration. As with the regulations for motor vehicles, the aircraft emissions standards will likely take some time to develop and finalize, with input from a range of stakeholders.