In 1968, Leonov was selected to be commander of a circumlunar Soyuz 7K-L1 flight. This was cancelled because of delays in achieving a reliable circumlunar flight (only the later Zond 7 and Zond 8 members of the programme were successful) and the Apollo 8 mission had already achieved that step in the Space Race. He was also selected to be the first Soviet person to land on the Moon, aboard the LOK/N1 spacecraft. This project was also cancelled. (The design required a spacewalk between lunar vehicles, something that contributed to his selection.) Leonov was to have been commander of the 1971 Soyuz 11 mission to Salyut 1, the first crewed space station, but his crew was replaced with the backup after one of the members, cosmonaut Valery Kubasov, was suspected to have contracted tuberculosis (the other member was Pyotr Kolodin).