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The criteria for what constitutes human spaceflight vary. The Fédération Aéronautique Internationale (FAI) Sporting Code for astronautics recognizes only flights that exceed an altitude of 100 kilometers (62 mi). In the United States, professional, military, and commercial astronauts who travel above an altitude of 50 miles (80 km) are awarded astronaut wings.

As of 17 November 2016, a total of 552 people from 36 countries have reached 100 km (62 mi) or more in altitude, of which 549 reached low Earth orbit or beyond. Of these, 24 people have traveled beyond low Earth orbit, either to lunar orbit, the lunar surface, or, in one case, a loop around the Moon. Three of the 24–Jim Lovell, John Young and Eugene Cernan–did so twice. The three current  astronauts who have flown without reaching low Earth orbit are spaceplane pilots Joe Walker, Mike Melvill, and Brian Binnie, who participated in suborbital missions.

As of 17 November 2016, under the U.S. definition, 558 people qualify as having reached space, above 50 miles (80 km) altitude. Of eight X-15 pilots who exceeded 50 miles (80 km) in altitude, only one exceeded 100 kilometers (about 62 miles). Space travelers have spent over 41,790 man-days (114.5 man-years) in space, including over 100 astronaut-days of spacewalks.




Mark