[7] The Korean War had commenced, and his deferment from the draft expired when he graduated from Jackson Junior College.

[6] He received his pilot wings and regular commission as a second lieutenant in the USAF in May 1952 at Williams Air Force Base, Arizona, and completed combat crew training in November 1952.

[7] He flew 145 combat missions in Korea in F-80 Shooting Stars and F-86 Sabres with the 35th Fighter-Bomber Squadron,[7] and earned two Distinguished Flying Crosses.

[6] McDivitt returned to the United States in September 1953 and served as pilot and assistant operations officer with the 19th Fighter Interceptor Squadron at Dow Air Force Base, Maine.

In November 1954, he entered advanced flying school at Tyndall Air Force Base, Florida, and in July 1955 went to McGuire Air Force Base, New Jersey, where he served as pilot, operations officer, and later as flight commander with the 332d Fighter Interceptor Squadron.

[1][6] After graduation, he went to Edwards Air Force Base, California, as a student test pilot in June 1959.

[10] This included flying as a chase pilot for Robert M. White's North American X-15 flight on July 17, 1962, in which White reached an altitude of 59.5 miles (95.8 km) and became the first X-15 pilot to be awarded Astronaut Wings based on the USAF definition of space as starting at 50 miles (80 km).

[11][a] McDivitt was in line to fly the X-15 when White left, and to head the project office for testing the McDonnell F-4 Phantom II, but he heard that NASA was looking to select a second group of astronauts to augment the Mercury Seven, and, after some thought, he decided to apply.

[17] The mission objectives were ill-defined at first, but consideration was given to performing extravehicular activity (EVA), space rendezvous and orbital station-keeping.

As a result, NASA management agreed to ensure that the Gemini space suit for the mission was capable of being used for EVA.

Kenneth S. Kleinknecht told the July 1964 press conference that announced the mission that one of the crew might open the hatch and stick his head outside, but this attracted little attention.

[19] The mission lasted 97 hours and 56 minutes, and made 62 orbits,[20] The first objective was to attempt the first space rendezvous with the spacecraft's spent Titan II launch vehicle's upper stage.

The orbital mechanics of rendezvous were not yet well understood by NASA engineers or astronauts; catching up to something requires slowing down.

[21] McDivitt finally broke off the rendezvous attempt in order to save propellant and preserve the second objective, which was for White to perform the first United States EVA.

McDivitt had spent some time before the flight with a McDonnell engineer, improvising a technique of forcing the gears to mesh by inserting the fingers inside the mechanism.

The hatch was difficult to open and also to relatch during the flight, but McDivitt was able to get it working both times, with his hands in his pressurized space suit gloves.

[22] On the second day, over Hawaii, while White was asleep, McDivitt happened to see an unidentified flying object (UFO), which he described as looking "like a beer can or a pop can, and with a little thing like maybe like a pencil or something sticking out of it".

On the way down, McDivitt struggled with a stuck thruster, but eventually slowed and ultimately halted the roll rate.

The spacecraft overshot its landing point by 80 kilometres (50 mi), but the astronauts were soon reached by the recovery ship, the USS Wasp.

[25] Later that week they traveled to the White House where Johnson presented them with the NASA Exceptional Service Medal.

[26] They were given a ticker tape parade in Chicago, and went to the 1965 Paris Air Show, where they met cosmonaut Yuri Gagarin.

It was hoped that the Saturn V would be available by the end of the year, and it would be flown as a third mission with Borman as CDR and Group 3 astronauts Michael Collins and Bill Anders.

[35] Apollo 9, McDivitt's ten-day Earth orbital Lunar Module test mission, lifted off on March 3, 1969.

After McDivitt and Schweickart inspected the tunnel connecting the CSM and LM, the assembled spacecraft separated from the S-IVB.

On the fourth day, Schweickart donned the Primary Life Support System, the backpack that astronauts would later wear on lunar surface EVAs, and exited the LM.

The next day, Scott undocked, and McDivitt flew the LM, putting the spacecraft's descent engine through its paces.

[42] McDivitt retired from the USAF and left NASA in June 1972, to take the position of Executive Vice President, Corporate Affairs for Consumers Power Company.

His recreational interests included hunting, fishing, golf, water sports, tennis, and all outdoor activities.