Launch was planned for April 12, 1971, to coincide with the 10th anniversary of Yuri Gagarin’s flight on Vostok 1, but technical problems delayed it until the 19th. The first crew launched later in the Soyuz 10 mission, but they ran into troubles while docking and were unable to enter the station; the Soyuz 10 mission was aborted and the crew returned safely to Earth. A replacement crew launched in Soyuz 11 and remained on board for 23 days. This was the first time in the history of spaceflight that a space station had been manned, and a new record time was set in space. This success was, however, short-lived when the crew was killed during re-entry, as a pressure-equalization valve in the Soyuz 11 re-entry capsule had opened prematurely, causing the crew to asphyxiate. They were the first and, as of 2019, the only humans to have died in space. After this accident, all missions were suspended while the Soyuz spacecraft was redesigned. The station was intentionally destroyed by de-orbiting after six months in orbit, because it ran out of fuel before a redesigned Soyuz spacecraft could be launched to it.