In June 1960, Borman was selected for Class 60-C at the USAF Experimental Flight Test Pilot School at Edwards Air Force Base in California, and became a test pilot. His class, which included Michael Collins and James B. Irwin, who also later became astronauts, graduated on April 21, 1961. Thomas P. Stafford, another future astronaut, was one of the instructors. On graduation, Borman was accepted as one of five students in the first class at the Aerospace Research Pilot School, a postgraduate school for test pilots to prepare them to become astronauts. Fellow members of the class included future astronaut Jim McDivitt. Classes included a course on orbital mechanics at the University of Michigan, and there were zero-G flights in modified Boeing KC-135 Stratotanker and Convair C-131 Samaritan aircraft. Borman introduced training with the Lockheed F-104 Starfighter. It would be flown up to , where the engine would cut out for lack of oxygen, and then coast up to . This would be followed by a powerless descent, and restarting the engine on the way down. A pressure suit was required.