The criteria for determining who has achieved human spaceflight vary. The FAI defines spaceflight as any flight over 100 kilometres (62 mi) of altitude. In the United States, professional, military, and commercial astronauts who travel above an altitude of 80 kilometres (50 mi) are eligible to purchase astronaut wings. Until 2003, professional space travelers were sponsored and trained exclusively by governments, either by the military or by civilian space agencies. However, with the first sub-orbital flight of the privately-funded Scaled Composites Tier One in 2004, the commercial astronaut category was created.