Canceled Apollo missions Schirra's crew would fly the C mission, first manned CSM (Block II CSM-101, retrofitted with the cabin safety improvements) as Apollo 7 in October 1968. McDivitt's crew and mission were kept as the first manned development LM flight (D mission); this was planned to be Apollo 8 in December 1968, now using a single Saturn V launch vehicle instead of two separate Saturn IB launches. The E mission was planned as an elliptical medium Earth orbit test of the operational LM with the CSM in a simulated lunar mission to an apogee of , to be commanded by Frank Borman
Apollo 4 the first mission to fly under the official Apollo mission numbering scheme approved by Mueller on April 24, 1967. Since the failed first manned flight had been designated Apollo 1 in honor of the crew widows' wishes, and three unmanned Apollo/Saturn IB flights had already occurred, Mueller resumed the numbering sequence at Apollo 4. The vehicle's on-pad, pre-launch tests and preparation practice started in September, and encountered several problems with propellant loading and various equipment failures. These pushed the launch into November, but provided valuable lessons learned on the new vehicle. By this time, North American had been purchased by