This is a list of astronauts by year of selection, people selected for training for a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft. Until recently, astronauts 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 SpaceShipOne in 2004, a new category of astronaut was created – the commercial astronaut. More than 500 people have trained as astronauts.