White was selected as a member of the astronaut team by NASA in September 1962. He was pilot for Gemini 4, which was a 66-revolution, 4-day mission that launched on June 3, and ended on June 7, 1965. He was outside Gemini 4 for 21 minutes. Other highlights of the mission included cabin depressurization, the opening of cabin doors, and 12 scientific and medical experiments. He was awarded the NASA Exceptional Service Medal and U.S. Air Force Senior Astronaut Wings. On March 21, 1966, he was named one of the pilots of the AS-204 mission, the first 3-man Apollo flight. Tragically, he died on January 27, 1967, in the Apollo spacecraft flash fire during a launch pad test at Kennedy Space Center, Florida.