In 1975, Stafford was the commander of the Apollo-Soyuz Test Project (ASTP) flight, the first joint U.S.-Soviet space mission. A brigadier general at the time, he became the first general officer to fly in space. He was the first member of his Naval Academy class to pin on the first, second, and third stars of a general officer. He made six rendezvous in space and logged 507 hours of space flight.
Stafford has flown more than 120 types of fixed-wing and rotary aircraft and three types of spacecraft. Since the deaths of Wally Schirra, Eugene Cernan, and John Young, he is the last surviving crew member of Gemini 6A, Gemini 9A, and Apollo 10. He and Vance Brand are the last two surviving crew members of ASTP.