Donald "Deke" Slayton was one of the original Mercury 7 astronauts — but he never flew in that program. Because of a heart condition, he was grounded for decades before being approved and flying in the Apollo-Soyuz Test Project, the first joint mission with the Soviet Union.
Slayton first got his wings in April 1943 and subsequently undertook dozens of combat flights in Europe and Japan during World War II. He then left the Air Force to study aeronautical engineering, worked at Boeing Aircraft Co. for two years, and then joined the Minnesota Air Guard in 1951, according to NASA.
