Stapp entered the U.S. Army Air Forces on 5 October 1944 as a physician and qualified as a flight surgeon.

[4] His first assignment included a series of flights testing various oxygen systems in unpressurized aircraft at 40,000 ft (12.2 km).

Stapp's work resolved that problem as well as many others, which allowed the next generation of high-altitude aircraft and the HALO insertion techniques.

[5] In 1967, the Air Force loaned Stapp to the National Highway Traffic Safety Administration to conduct auto-safety research.

As early as 1945, service personnel realized the need for a comprehensive and controlled series of studies into the effects of deceleration on the human body.

As a result of Stapp's findings, the acceleration requirement for fighter seats was increased considerably up to 32 g (310 m/s²).

His work showed that a pilot could walk away from crashes when properly protected by harnesses if the seat does not break loose.

It was made of nylon mesh webbing, fit snugly over the shoulder facing the forward part of the aircraft.

He said "I felt a sensation in the eyes, somewhat like the extraction of a molar without anesthetic," but his survival without any permanent injuries supported the development of further safety technologies including the ejection seat.

[11] Also developed by Stapp as an added safety measure was an improved version of the currently used shoulder strap and lap belt.

The leg and shoulder straps and the lap belt all fastened together at one point, and pressure was distributed evenly over the stronger body surfaces, rather than on the solar plexus, as was the case with the old harness.

Stapp stayed with his aircraft at a speed of 570 mph (920 km/h) with the canopy removed, and suffered no injurious effects from the wind blasts.

Stapp was an inveterate collector of aphorisms and adages, kept a logbook of such, and the practice spread to his entire working group.

"[14] In 1957, he was presented with the Gorgas Medal from the Association of Military Surgeons of the United States (AMSUS).

The award recognizes individuals for their significant role in the history of Air Force space and missile programs.