So the F-22 Raptor fleet has been grounded by Air Combat Command boss Gen. Robert Fraser due to problems with the aircraft's oxygen generating system, the same flaw that has kept the jets restricted to flights under 25,000 feet since January. The system has been under investigation since shortly after the late November crash of an F-22 in Alaska. The total grounding was apparently due to numerous reports of pilots suffering from a lack of oxygen while flying the jet since the restriction was put in place. It should be noted that at 25,000 feet its almost impossible for an unacclimatized person to breathe normally. Capping flights at that altitude would theoretically allow a pilot to more quickly dive to a lower altitude where he could breathe without the oxygen system's help. The jets have been gounded indefinitely until the problem is solved, according to numerous reports. If they've been looking at this since November, it has to be a pretty tricky problem. You can also be sure that speculation will emerge that problems with the oxygen generator system played a role in the Air Force's much-discussed decision to keep the F-22s out of the fight in Libya.
While the Air Force says it could scramble F-22 crews in case of an emergency that warrants the need for the jets, pilots will train on simulators until the restriction is lifted.