The world's fastest jet aircraft. A Lockheed SR-71 'Blackbird' in flight. The aircraft seen here is the two-seat SR-71B used to train pilots. This aircraft, with two others, was delivered to NASA after retirement from the US Air Force. Its military use was as a high-speed photographic reconnaissance aircraft. In NASA's hands, it will be used to investigate high-speed aerodynamics in support of the X-30 National Aero Space Plane (NASP) project. Developed at the Lockheed insSkunk Worksins in the early 1960s, the first SR-71 flew on 22 December 1964. Although exact figures are classified, it is known that the SR-71 can cruise at over 3300 km/h (Mach 3.2) at 35,000 metres.