Soyuz 18a

Soyuz 18a (Russian: Союз 18a, Union 18a) (also called Soyuz 18-1 and the April 5 Anomaly) was a manned Soyuz spacecraft launched by the Soviet Union in 1975, intended to dock with the orbiting Salyut 4 space station, but which failed to achieve orbit due to a serious malfunction during launch. The crew consisted of commander Vasili Lazarev, an Air Force major, and flight engineer Oleg Makarov, a civilian.

The accident was disclosed by the normally secretive Soviets as it occurred during preparations for their joint Apollo-Soyuz Test Project with the United States which flew three months later. The crew, who feared initially they had landed in China, were successfully recovered.