Aviation is the most carbon-intensive form of travel and is a significant contributor to climate change. International aviation emissions are growing rapidly and are projected to grow 300% by 2050 if no action is taken. A 2016 report has shown that, in order for international aviation to only consume 12% of the carbon budget that would allow the world to stay within a 1.5°C temperature increase by 2050, the absolute maximum of innovation, operational improvements, and biofuels must be deployed. An ambitious policy to reduce aviation emissions is urgently needed. The United States has not enacted any emissions reduction measures for aviation. There are no substantive legal barriers to the United States doing so, but there are significant political challenges, including strong opposition from the aviation industry and differences of views among the agencies that regulate aviation in the United States, especially EPA and the Federal Aviation Administration (FAA). The International Civil Aviation Organization (ICAO) has been discussing the regulation of aviation emissions for two decades. And within the industry itself, there are a number of efficiency goals and some airlines are beginning to test biofuels. However, the sum of all these efforts will be inadequate to reduce aviation emissions by two-thirds by 2050, as is envisaged in the DDPP reports. The chapter sets forth a variety of measures that, when combined, could put the United States on track to reduce aviation emissions by two-thirds by 2050.