Soyuz 11 is launched. The mission ends in disaster when all three cosmonauts, Georgy Dobrovolsky, Vladislav Volkov, and Viktor Patsayev are suffocated by uncontrolled decompression of the capsule during re-entry on 29 June.

Soyuz 11 was the only crewed mission to board the world's first space station, Salyut 1. The crew, Georgy Dobrovolsky, Vladislav Volkov, and Viktor Patsayev, arrived at the space station on 7 June 1971, and departed on 29 June 1971. The mission ended in disaster when the crew capsule depressurised during preparations for re-entry, killing the three-person crew. The three crew members of Soyuz 11 are the only humans to have died in space.

Georgy Timofeyevich Dobrovolsky was a Soviet cosmonaut who commanded the three-man crew of the Soyuz 11 spacecraft. They became the world's first space station crew aboard Salyut 1, but died of asphyxiation because of an accidentally opened valve. They were the first and only humans to have died in space.

Vladislav Nikolayevich Volkov was a Soviet cosmonaut who flew on the Soyuz 7 and Soyuz 11 missions. The second mission terminated fatally. Volkov and the two other crew members were asphyxiated on reentry, the only three people to have died in outer space.

Viktor Ivanovich Patsayev was a Soviet cosmonaut who flew on the Soyuz 11 mission and was part of the third space crew to die during a space flight. On board the space station Salyut 1 he operated the Orion 1 Space Observatory ; he became the first man to operate a telescope outside the Earth's atmosphere.

An uncontrolled decompression is an undesired drop in the pressure of a sealed system, such as a pressurised aircraft cabin or hyperbaric chamber, that typically results from human error, structural failure, or impact, causing the pressurised vessel to vent into its surroundings or fail to pressurize at all.