Gemini 4 was a 4-day, 66-orbit mission launched on June 3, 1965. Highlights of the mission included a controlled extra-vehicular activity period and a number of experiments.
On June 3, 1965, Gemini-4 was launched into orbit 150 miles above the Earth's surface. Rookie astronauts McDivitt and White were headed for the USA's first long-duration flight, the first to attempt extensive visual observations and photography. On the second day, over Hawaii, the 35-year-old McDivitt reported seeing an object -- "like a beer can with an arm sticking out" -- which NASA officials later announced had been identified by Air Force space radars as the thousand-mile-distant Pegasus-2 (but that range was too great, it turned out, for McDivitt's object to have been the winged Pegasus satellite). Together with a mysterious "tadpole" photo, the McDivitt report has achieved UFO superstardom and has been firmly enshrined in UFO literature and lore. Gordon Cooper wrote in his memoirs that as far as he knows, it is the only officially reported account of a UFO in any of the Mercury, Gemini or Apollo missions. McDivitt believes what he saw was a reflection of bolts in the multipaned windows.
After Gemini 4, he, along with Astronaut Group 3 astronauts David Scott and Russell Schweickart were named as members of the backup crew to the ill-fated Apollo 1 mission, but were replaced by Walter Schirra, Donn Eisele, and Walter Cunningham as backups and instead, were named prime crew members of the Apollo 2 mission. After the Apollo 1 fire, the backup Apollo 1 crew flew as the prime crew for Apollo 7 and McDivitt served as commander of Apollo 9, a 10-day earth orbital flight launched on March 3, 1969. Originally to be the second manned flight, as Apollo 8, the Lunar Module that was having problems and with the possibilities of a Soviet Moonshot by the end of 1968, NASA decided to make Apollo 8 a circumlunar flight, but flight operations director Deke Slayton preferred McDivitt and his crew stick with the LM test flight, and McDivitt agreed. The revised Apollo 8 flight went to Frank Borman, Jim Lovell, and William Anders, and the Earth-orbital LM test flight became Apollo 9. In a BBC documentary "NASA: Triumph and Tragedy", Jim McDivitt said that they had no idea how 100% oxygen atmosphere would influence burning (regarding Apollo 1 fire).
After Apollo 9, McDivitt became Manager of Lunar Landing Operations in May 1969, and led a team that planned the lunar exploration program and redesigned the spacecraft to accomplish this task. In August 1969, he became Manager of the Apollo Spacecraft Program and was the program manager for Apollo 12, 13, 14, 15 and 16. He would have been slated to fly to the moon as Lunar Module Pilot for the Apollo 14 flight, but a fall-out with Shepard (who was the number two astronaut after Deke Slayton), as well as an attempt to ground Gene Cernan, the backup Apollo 14 commander and later the Apollo 17 commander, led to his resignation as Apollo Program Manager .