Space Shuttle prototype Enterprise atop NASA's first Shuttle Carrier Aircraft (SCA), NASA 905, during the first of the shuttle program's Approach and Landing Tests (ALT) at the Dryden Flight Research Center, Edwards, California on February 18, 1977.  The first flight of the program consisted of the Space Shuttle Enterprise attached to the Shuttle Carrier Aircraft to determine how well the two vehicles flew together. Five "captive-inactive" flights were flown with no crew in the Enterprise.

Photo and caption credit: NASA Dryden Flight Research Center