Buzz Aldrin on July 20, Aldrin and Armstrong entered "Eagle", and began the final preparations for lunar descent. At 17:44:00 "Eagle" separated from the "Columbia". Collins, alone aboard "Columbia", inspected "Eagle" as it pirouetted before him to ensure the craft was not damaged, and that the landing gear was correctly deployed. Throughout the descent, Aldrin called out navigation data to Armstrong, who was busy piloting the "Eagle". Five minutes into the descent burn, and above the surface of the Moon, the LM guidance computer (LGC) distracted the crew with the first of several unexpected alarms that indicated that it could not complete
Buzz Aldrin Pilot as the first to step onto the lunar surface. However, when Aldrin learned that this might be amended, he lobbied within NASA for the original procedure to be followed. Multiple factors contributed to the final decision, including the physical positioning of the astronauts within the compact lunar lander, which made it easier for Armstrong to be the first to exit the spacecraft. Furthermore, there was little support for Aldrin's views among other senior astronauts who would command later Apollo missions, and who may have been the first to make a lunar landing had Apollo 11 failed. Collins has commented