Jim Lovell and Aldrin were selected as the backup crew of Gemini 10 , commander and pilot respectively . Backup crews usually became the prime crew of the third following mission , but the last scheduled mission in the program was Gemini 12 . The February 28 , 1966 , deaths of the Gemini 9 prime crew , Elliot See and Charles Bassett , in an air crash , led to Lovell and Aldrin being moved up one mission to backup for Gemini 9 , which put them in position as prime crew for Gemini 12 . They were designated its prime crew on June 17 , 1966 , with Gordon Cooper and Gene Cernan as their backups
air crash
1966 NASA T-38 crash
Buzz Aldrin