The United States has an extensive air transportation network. In 2013, there were 86 airports in the U.S. that annually handled over 1,000,000 passengers each and eight of the world's thirty busiest airports by passenger volume in 2020 were in the U.S. (down from 12 in 2014), including the world's second busiest, Hartsfield-Jackson Atlanta International Airport. In 2012, 88% of all traffic was through the 62 busiest airports in the country. In terms of cargo, in 2015, eight of the world's thirty busiest airports were in the U.S., including the world's second busiest, Memphis International Airport, behind only Hong Kong International Airport in China. Private aircraft are also used for medical emergencies, government agencies, large businesses, and individuals, see general aviation.