The space shuttle Enterprise is seen mated on top of the NASA 747 Shuttle Carrier Aircraft (SCA) at Washington Dulles International Airport, Friday, April 20, 2012, in Sterling, Va. Enterprise, the first orbiter built for the Space Shuttle Program, was used primarily for ground and flight tests within the atmosphere. The initial testing period named Approach and Landing Test (ALT) included a flight on February 18, 1977 atop a Shuttle Carrier Aircraft (SCA) to measure structural loads and ground handling and braking characteristics of the mated system. Enterprise will go on permanent display at the Intrepid Sea Air and Space Museum in New York in June. Photo Credit: (NASA/Bill Ingalls)
