The United States has advanced air transportation infrastructure which utilizes approximately 5,000 paved runways. In terms of passengers, seventeen of the world's thirty busiest airports in 2004 were in the United States, including the world's busiest, Hartsfield-Jackson Atlanta International Airport. In terms of cargo, in the same year, twelve of the world's thirty busiest airports were in the United States, including the world's busiest, Memphis International Airport.[24] Private aircraft are also used for medical emergencies, government agencies, large businesses, and individuals, see general aviation.