Having commenced its maiden flight in December 1968, just two months before the Concorde, the Tupolev TU-144, with a maximum speed slightly greater than Mach 2, is recognized as the first supersonic commercial aircraft, and was in operation from 1968 until 1999, with a total of 16 aircraft having been produced from 1967 until 1983. Although the TU-144 went into commercial passenger service with Aeroflot in late 1975, it was retired from passenger service in 1978 and used as a commercial cargo transport until 1983, when it was then used by the Soviet Space Program to train pilots, followed by NASA, who used the aircraft for supersonic research until it was finally retired from service in 1999.