Initially, Aldrin thought that he would be first to walk on the Moon, based on the experience of Gemini; during that program, the pilot conducted the EVAs while the command pilot, who had greater responsibilities and less time to train for an EVA, stayed on board. However, when that actual procedure was tried with suited-up astronauts in an Apollo LM mockup, the LM was damaged – in order for Aldrin (LM Pilot) to get out first, he had to climb over Armstrong (commander) to get to the door.
A March 1969 meeting between Slayton, George Low, Bob Gilruth, and Chris Kraft determined that Armstrong would be the first person on the Moon, in some part because NASA management saw Armstrong as a person who did not have a large ego. A press conference held on April 14, 1969 gave the design of the LM cabin as the reason for Armstrong being first; the hatch opened inwards and to the right, making it difficult for the lunar module pilot, on the right-hand side, to egress first. Slayton added, “Secondly, just on a pure protocol basis, I figured the commander ought to be the first guy out. . . . I changed it as soon as I found they had the time line that showed that. Bob Gilruth approved my decision.” At the time of their meeting, the four men did not know about the hatch issue.