Apollo 20

Several planned missions of the Apollo crewed Moon landing program of the 1960s and 1970s were canceled, for reasons which included changes in technical direction, the Apollo 1 fire, the Apollo 13 incident, hardware delays, and budget limitations. After the landing by Apollo 12, Apollo 20, which would have been the final crewed mission to the Moon, was canceled to allow Skylab to launch as a "dry workshop". The next two missions, Apollo 18 and Apollo 19, were later canceled after Apollo 13 and further budget cuts. Two Skylab missions also ended up being canceled. Two complete Saturn V rockets remained unused and were put on display in the United States.