 This system provided valuable experience for future X-15 pilots and astronauts in spacecraft control and maneuverability.The trials began in 1959 and concluded in 1961, after which the aircraft was used for other NASA purposes until it was retired in November 1975.Between August and October 1963, Lockheed delivered three single-seat F-104G Starfighters to NASA, designated F-104N, for use as high-speed chase aircraft.