When was the first joint US-Soviet space flight?

The Apollo–Soyuz Test Project conducted in July 1975, was the first joint U.S.–Soviet space flight.

Its primary purpose was as a symbol of the policy of détente.

The mission included both joint and separate scientific experiments (including an engineered eclipse of the Sun by Apollo to allow Soyuz to take photographs of the solar corona), and provided useful engineering experience for future joint US–Russian space flights, such as the Shuttle–Mir Program and the International Space Station.