Answer
Vance Brand is Stafford's only remaining Apollo-Soyuz Test Project crew member. Stafford and Brand were the two astronauts who flew the Apollo 10 mission in May 1969, which was the final test flight of the Apollo spacecraft before the Apollo 11 mission landed on the Moon. Brand then flew the Apollo-Soyuz Test Project in July 1975, which was the first joint US-Soviet space mission.