The world's fastest jet aircraft. A Lockheed SR-71 'Blackbird' taxying past an F-18 fighter shortly after landing. The small open hatch doors near the SR-71's tail show that the braking parachute has been used. This aircraft, with two others, was delivered to NASA after retirement from the US Air Force. 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 in the early 1960s, the first SR-71 flew on 22 December 1964. Although exact figures are still classified, it is known that the SR-71 can cruise at over 3300 km/h (Mach 3.2) at altitudes in excess of 35,000 metres.