Stafford first flew on Gemini 6A, which achieved the first crewed rendezvous — open definition in space with Gemini 7. He then commanded Gemini 9A after the original crew died in a training accident, gaining experience with rendezvous and EVA — open definition challenges. On Apollo 10, Stafford commanded the full lunar landing rehearsal, flying the lunar module Snoopy with Gene Cernan down to low altitude above the Moon while John Young remained in lunar orbit.

In 1975, Stafford commanded the American crew of the Apollo-Soyuz Test Project, docking with a Soviet Soyuz spacecraft in orbit and helping create one of the most visible moments of Cold War space cooperation. He also served as Chief of the Astronaut Office and later retired from the Air Force as a lieutenant general. His career linked Gemini operations, Apollo lunar testing, and the first joint United States-Soviet crewed mission.

Stafford's background fit the broader pattern of the early astronaut corps: technical training, operational discipline, and a career built around difficult work before spaceflight. His formal education included United States Naval Academy (B.S. Naval Science, 1952). His service background is recorded as Lieutenant General, United States Air Force. His personal record also sits alongside a family life recorded as two marriages, four children, a reminder that these careers unfolded within ordinary lives as well as national history.