Throughout NASA’s historic space shuttle program, a total of 6 shuttles were constructed- but not all of them were capable of spaceflight. The first shuttle, called Enterprise, was originally designed as a test model to be used in practiced landing exercises in the 1970’s.
Named after the famed fictional ship from the hit TV series “Star Trek”, the Enterprise rolled out with great fanfare, including a contingent of actors from the show. Glide/landing tests in August & September of 1977 proved successful, and Enterprise was scheduled to be fully outfitted with heat shields and engines- making it capable of space flight.
However, changes in design recommendations eventually led to the construction of a more efficient shuttle, Columbia. So Enterprise never got its chance to reach space- but its place in history was secured.