NASA's space shuttle fleet was comprised of orbiters Atlantis, Challenger, Columbia, Discovery, Endeavour and a prototype craft named Enterprise. The space shuttle program began in 1981 and conducted 135 missions.
NASA's space shuttle was the world's first reusable spacecraft and was designed to carry astronauts and equipment into orbit. The first two shuttles constructed, Columbia and Challenger, were both lost during missions. NASA's remaining shuttles were officially retired in 2011, with the remaining three shuttles placed on permanent public display. As of 2014, they remain at California Science Center, the Smithsonian's Steven F. Udvar-Hazy Center and the Kennedy Space Center.