destroyed and one crew member drowned. The project was subsequently abandoned. During the development of the Space Shuttle orbiter in the 1970s, NASA used two modified Boeing 747 airliners, known as the Shuttle Carrier Aircraft, to launch the Space Shuttle Enterprise, a crewed atmospheric test vehicle used to test the orbiter's approach and landing capabilities. These aircraft were subsequently used throughout the Space Shuttle Program to transport the shuttles across long distances. The Pegasus launch vehicle became the first air-launched orbital rocket when it was launched on April 5, 1990 by the private company Orbital Sciences Corporation (now a part of Northrop Grumman), from a NASA-owned B-52 Stratofortress. It has flown more than 40 times since, launched mostly from the company's own Lockheed L-1011 known as Stargazer. Orbital Sciences was developing the Pegasus II launcher that would have dropped from the purpose-built Scaled Composites Stratolaunch; capacity to low Earth orbit was projected to be In the early 2000s, the B-52 was used to launch the X-43 hypersonic testbed aircraft. Recently, the air launch method has gained popularity with commercial launch providers. The Ansari X-Prize $10 million purse was won by a team led by Burt Rutan's Scaled Composites, launching the SpaceShipOne from the purpose-built White Knight carrier aircraft. AirLaunch LLC developed QuickReach small satellite launch system that validated the concept by dropping a test payload in-flight from the cargo bay of an unmodified C-17 aircraft. Other commercial enterprises developing air launch systems for spaceflight include Stratolaunch Systems, Generation Orbit, which plans to use a Learjet 35 aircraft to launch orbital, suborbital and atmospheric rockets. Virgin Orbit is developing the uncrewed satellite launcher LauncherOne and Virgin Galactic the suborbital crewed spacecraft SpaceShipTwo, the latter as a technological successor to SpaceShipOne. See also Composite aircraft Parasite aircraft Mother ship Pegasus (rocket) Air launch to orbit Airborne aircraft carrier References External links A Study of Air Launch Methods for RLVs (AIAA 2001) Launch Missile operation Rocketry