Normal air contains about 21 percent oxygen. The moment F-22 pilots strap on their air masks, they're breathing 60 percent oxygen. Within the seconds it takes the plane to reach 11,000 feet after takeoff, the pilot is breathing air that's 93 percent oxygen.
But that's far more than the body needs except at the highest altitudes and in high-G-force maneuvers, some experts say.
As the aircraft accelerates and the rich oxygen is forced into the lungs and can't be absorbed, it creates a condition called "acceleration atelectasis," in which alveoli, which transmit oxygen to the blood and remove carbon dioxide, collapse.
That causes breathing to become more labored as pilots maneuver at high speeds, with high G-forces hampering the blood supply. Their blood can't get rid of the carbon dioxide and can't get oxygen to the body's organs.
That could explain the disorientation and dizziness reported by pilots. It's almost like being intoxicated.
"If you get enough of that, you could certainly pass out," said Paul McDonough, an associate professor of kinesiology at the University of Texas at Arlington.
In addition to alveoli collapse, the body needs CO2 to gauge breathing regulation. Obviously, the USAF still has work to do.
