Apollo 9 to land on the Moon; when the crews for Apollo 8 and 9 were swapped, their backup crews were also swapped. Since the rule of thumb was for backup crews to fly as prime crew three missions later, this put Neil Armstrong's crew (Borman's backup) in position for the first landing mission Apollo 11 instead of Pete Conrad's crew, who made the second landing on Apollo 12. Apollo 9 was the first space test of the complete Apollo spacecraft, including the third critical piece of Apollo hardware besides the command and service module and the Saturn V launch vehicle—the lunar
Apollo 4 NASA in the Apollo spacecraft, also built by North American. The mission was the first Apollo flight after the stand-down imposed after the Apollo 1 fire which killed the first Apollo crew. It was the first to use NASA's official Apollo numbering scheme established in April 1967, designated Apollo 4 because there had been three previous unmanned Apollo/Saturn flights in 1966, using the Saturn IB launch vehicle. The mission lasted almost nine hours, splashing down in the Pacific Ocean, achieving all mission goals. NASA deemed the mission a complete success, because it proved the Saturn V worked, an important step