1st man to go into space died while training for 2nd mission
Soviet cosmonaut Yuri Gagarin, who became the first man to go into space in 1961, died aboard an MiG fighter plane on March 27, 1968, while training for a second space mission. Documents declassified in 2011 said the plane entered a high-speed spin after trying to avoid a weather balloon and crashed. Rumours, however, claim Gagarin was drunk while flying.