The world's first supersonic jet aircraft trainer and the world’s most produced. Developed by the US manufacturing company Northrop, it is used by NASA to prepare astronauts for space flight. Its high-g and low-g manoeuvres accustom astronauts to the conditions occurring during the ascent of a launch vehicle, the free-fall atmosphere of space, and re-entry. The T-38 flights are taken about three days before launch. The US Air Force's first T-38A ‘Talon’ jet trainer flew on 10 April 1959 and entered service on 17 March 1961 as the force's first supersonic trainer.