(CBS News) The F-22 Raptor is America's most advanced fighter plane. It ought to be: Each one costs $143 million.
However, for months something mysterious has been happening to F-22 pilots in flight, putting them in jeopardy.
The F-22 is on a very short leash. After first being grounded, the world's most sophisticated and expensive jet fighter is flying again, but limited to flights within 30 minutes of a landing field.
The reason: A mysterious problem that without warning has caused pilots to suffer hypoxia - become disoriented from lack of oxygen. Over the past 10 months, says Col. Kevin Robbins, commander of the First Fighter Wing at Langley Air Force Base in Virginia, there have been 11 incidents of hypoxia.
"No one has gotten to the point where they're completely, where they're delirious. They're still able to function, still able to bring the aircraft back safely," Col. Robbins says.
CBS News correspondent David Martin experienced hypoxia first hand in an F-22 simulator as Maj. Tom Massa reduced the flow of oxygen to his mask. It is like being dizzy.
When it got too bad, Martin pulled the emergency oxygen, and only then did he realize how far downhill his ability to function had gone. When he thought his simulated flight was going straight and level, he was actually continuing to climb.
The real F-22 can pull 9 Gs, subjecting the pilot to a force nine times the weight of gravity.
One standard piece of equipment is an inflatable vest. It provides chest counter-pressure during rapid decompression.
Technical Sgt. Scott Bender helped Martin into a vest and hooked him up to an oxygen machine with the instructions: "Don't panic." The vest inflated to protect Martin's lungs from exploding at high altitude, but it also made it harder to breathe.
Centrifuge tests revealed that the vest - which was supposed to improve the pilot's chances of survival - was actually a hazard.
"The vest was inflating every time you pull G's in the aircraft and then staying inflated which was making it more difficult to take air," Col. Robbins says.
After months of dissecting every inch of the plane's complex oxygen system, Maj. Gen. Charles Lyon, the man in charge of the investigation, believes he has solved the mystery of the F-22: It's the vest.
F-22 pilots no longer wear the vest, but as a result are not allowed to fly above 44,000 feet. Even without the vest, there have been two cases of pilots running short of oxygen, although General Lyon says those were mechanical malfunctions unrelated to the hypoxia mystery. Until General Lyon can convince Defense Secretary Panetta he really has solved the mystery, the F-22 will remain on a short leash.
Below, watch the original "60 Minutes" report on the F-22's oxygen deprivation issues