This is a list of astronauts by year of selection: people selected to train 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 advent of suborbital flight starting with privately funded SpaceShipOne in 2004, a new category of astronaut was created: the commercial astronaut.