For the second time this year the Air Force has grounded dozens of F-22 Raptors, some of the world's most sophisticated and expensive stealth fighter jets, after another pilot appeared to suffer from a lack of oxygen mid-flight.
Air Force commands at two U.S. bases "paused" missions after an F-22 pilot at Joint Base Langley-Eustis in Virginia showed signs of hypoxia while in midair, Air Force spokesperson Lt. Col. John Haynes told ABC News.
The mission suspension comes just over a month after the $143 million-a-pop F-22s were cleared to go back in the air following a nearly five-month, nationwide grounding also because of mysterious oxygen problems. In announcing that grounding, Air Force officials said that in 12 separate incidents pilots had experienced "hypoxia-like symptoms" while flying the planes over the last three years. Hypoxia occurs when the brain does not receive enough oxygen and can cause dizziness, confusion and "poor judgment".
Though no culprit for the oxygen issue was found, the Air Force cautiously cleared the planes to go back in the air in September after investigating the life support systems because it had, according to Air Force Chief of Staff Gen. Norton Schwartz, "enough insight from recent studies and investigations that a return to flight [was] prudent and appropriate."
The U.S. has more than 160 F-22s stationed at a handful of bases across the country, but the current halt is only in effect at Langley and at Alaska's Joint Base Elmendorf-Richardson. Elmendorf-Richardson has not experienced an incident recently, but it is the home base of the late Capt. Jeffrey Haney who was killed in an F-22 crash during a nighttime training mission in November 2010. An investigation into that crash is ongoing, the Air Force said, but Schwartz told reporters last month the oxygen system was definitely not the cause of the crash, despite news reports to the contrary.
Along with the F-35 fighter, which is slightly less expensive per plane, the F-22 marks America's foray fifth-generation stealth fighter jets that the Air Force said can dominate the air space anywhere in the world -- even if they've never had to prove it.
Not a single one of the Raptors -- which cost U.S. government $77.4 billion for a total of 187 planes from developer Lockheed Martin, according to a report by the Government Accountability Office -- has been used in combat operations and isn't expected to "any time soon," an Air Force official told ABC News last month.
The Pentagon initially ordered more than 600 of the fifth-generation fighters, but Congress stopped at funding 187 in 2009 under a hail of criticism over the fact that the planes are designed to take on other rival high-tech fighter jets instead of the third-world militaries and insurgents the U.S. currently faces.
Only recently have rival major powers -- including Russia and China -- unveiled their prototypes for what are believed to be their own stealth fighters, designed to take on the F-22.
Since the nationwide grounding was lifted, Haynes said the F-22s have completed 1,300 training and homeland defense missions without incident, save for the one at Langley, and said that any halts at local bases are at the discretion of the base wing commanders there. There are currently no plans for another nationwide halt as other bases keep a close eye on their pilots' safety in the air.
"Everybody knows, everybody's watching," Haynes said.