Apollo-Soyuz was the last mission of the Apollo era. It was less a technical matter than it was a political one. In 1972 U.S. President Nixon and the Soviet leader Kosygin initiated the program. It was a symbol for the goodwill between the two superpowers.
American and Soviet scientists had to grant each other inside into their respective programs so that a common docking system could be designed. In preparation of the flight Soviet cosmonauts were practicing at Johnson space center, and the American crew did the same in Moscow. Flight controllers from both nations also conducted joint simulations.
Apollo 18 and Soyuz 19 left Earth within seven-and-a-half hours on July 15, 1975. Two days later Thomas P. Stafford and Alexei Leonov exchanged handshakes. The two space ships remained linked for 44 hours. During that time they ate together, exchanged gifts and flags and paid visits to each other's ships. They also conducted further docking maneuvers in which the Soyuz took over the role of the active ship. The Soviets spent five days in space. The Americans concluded their trip after nine days.