www.nasa.gov X-43A Raises the Bar to Mach 9.6 Guinness World Records recognized NASA's X-43A scramjet with a new world speed record for a jet-powered aircraft - Mach 9.6, or nearly 7000 mph. The X-43A set the new mark and broke its own world record on its third and final flight on Nov. 16, 2004. In March 2004, the X-43A set the previous record of Mach 6.8 (nearly 5000 mph). The fastest air-breathing, manned vehicle, the US Air Force SR-71, achieved slightly more than Mach 3.2. The X-43A more than doubled, then tripled, the top speed of the jet-powered SR-71. en.wikipedia.org The X-43 is an unmanned experimental hypersonic aircraft design with multiple planned scale variations meant to test different aspects of hypersonic flight. It is part of NASA's Hyper-X program. A winged booster rocket with the X-43 itself at the tip, called a "stack", is launched from a carrier plane. After the booster rocket (a modified first stage of the Pegasus rocket) brings the stack to the target speed and altitude, it is discarded, and the X-43 flies free using its own engine, a scramjet.