Apollo 8 yet ready to make its first flight. Astronaut Jim McDivitt's crew, who were training to fly the first lunar module flight in low Earth orbit, became the crew for the Apollo 9 mission, and Borman's crew were moved to the Apollo 8 mission. This left Borman's crew with two to three months' less training and preparation time than originally planned, and replaced the planned lunar module training with translunar navigation training. Apollo 8 took 68 hours (almost three days) to travel the distance to the Moon. The crew orbited the Moon ten times over the course of 20 hours, during
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