On December 5, the states of California, Connecticut, New Jersey, New Mexico and Pennsylvania, the District of Columbia, and a coalition of environmental groups filed a petition with the U.S. EPA requesting that it regulate the greenhouse gas emissions of aircraft under the Clean Air Act. The petition asks that EPA (1) make an explicit finding that greenhouse gas emissions from aircraft contribute to air pollution that may endanger public health and welfare, and (2) adopt regulations to control those emissions. According to an EPA inventory of greenhouse gas emissions in the United States, in 2005 aircraft emissions accounted for 3% of U.S. carbon dioxide emissions and 12% of transportation sector emissions.