Of the 439 astronauts that entered space up to the end of November 2004, 11 have died in training incidents and 18 have died in in-flight accidents. Of those 18, only the crew of Soyuz 11 in 1971 actually died in space. The USA sets the space-boundary at 50 miles high while the FAI defines space as starting at a height of 100 km. Challenger's last flight in 1986 never reached this height. Columbia broke apart on re-entry.

The crew of Soyuz 11, Georgi Dobrovolski, Viktor Patsayev and Vladislav Volkov, were killed after undocking from space station Salyut 1 after a three-week stay. A valve on their spacecraft had accidentally opened when the service module separated, which was only discovered when the module was opened by the recovery team. Technically the only fatalities in space (above 100 km).