Photo with Heroes of the Soviet Union of the USSR “Space flights”. In the photo there is Cosmonaut Leonov and other cosmonauts. An astronaut is a person who tests and operates space technology in space flight. The concept of space flight is different in different countries. According to the classification of the International Aeronautics Federation (FAI), a space flight is considered to be a flight whose altitude exceeds 100 km. According to the US Air Force classification, space flight is considered to be a flight whose altitude exceeds 50 miles (80 km 467 m). In Russia, space flight is an orbital flight, that is, a flight in which the device must make at least one revolution around the Earth. This is why the total number of astronauts differs in different sources.