The Apollo Lunar Module was a two-stage crewed spacecraft built by Grumman for operations in vacuum. Ten flight articles—LM-1, LM-3 through LM-8, and LM-10 through LM-12—flew from 1968 through 1972. The program progressed from uncrewed and Earth-orbit tests to a lunar-orbit dress rehearsal, six crewed lunar landings, and Apollo 13's lifesaving return to Earth.