In April 1966, McDivitt, Scott and Schweickart were selected by Director of Flight Crew Operations Deke Slayton as the second Apollo crew. Their initial job was as backup to the first Apollo crew to be chosen, Gus Grissom, Ed White, and Roger Chaffee, for the first crewed Earth orbital test flight of the block I command and service module, designated AS-204. Delays in the block I CSM development pushed AS-204 into 1967. The revised plan had the McDivitt crew scheduled for the second crewed CSM, which was to rendezvous in Earth orbit with an uncrewed LM, launched separately. The third crewed mission, to be commanded by Frank Borman, was to be the first launch of a SaturnV with a crew.