[1] John Aaron was born in Wellington, Texas, and grew up in rural Western Oklahoma near Vinson, one of the youngest of a family of seven children.

After spending a year attending Bethany Nazarene College, he transferred to Southwestern Oklahoma State University, from which he graduated in 1964 with a Bachelor of Science degree in Physics.

When he arrived at NASA, Aaron was trained as an EECOM, a flight controller with specific responsibility for the electrical, environmental and communications systems on board the spacecraft.

For the case that first drew his attention to the system, normal readings could be restored by putting the SCE on its auxiliary setting, which meant that it would operate even with low-voltage conditions.

Dick Gordon, a ground expert on the CSM as well as the Apollo 12 command module pilot, was familiar with both the location and the function of the SCE switch, and instructed Alan Bean to flip it to aux.

[1][3] Aaron was off duty when the Apollo 13 explosion occurred, but was quickly called to Mission Control to assist in the rescue and recovery effort.

Contrary to existing procedures, he ordered the instrumentation system, which included telemetry, visibility, and the transmitters for communications, to be turned on last, just before reentry, rather than first.

On February 12, 1993, he was forced to resign from the job after Texas Senator Robert Krueger blamed him for $500 million of overspending on the station project.

The 2015 science fiction film The Martian contains a reference to the "steely-eyed missile man" title bestowed on Aaron, as does the Legends of Tomorrow second-season episode "Moonshot".