(CBS News) Pilots flying the U.S. military's most advanced fighter jet, the F-22 Raptor, had been getting sick at the controls, and much of the focus toward finding the cause has been on the plane itself.
Now, however, Air Force investigators say the specialized flight suit pilots wear in the F-22 could be at least partially to blame for the oxygen deprivation experienced in flight.
On Thursday, the Air Force confirmed that reports of hypoxia are 10 times higher for F-22 pilots than in other USAF aircraft.
Officials tell CBS News correspondent David Martin that tests carried out in a flight-simulating centrifuge replicated hypoxia-like conditions for pilots wearing the suits. The link to the suits was first reported by CNN on Wednesday.
As "60 Minutes" reported in May (video), the Raptor - the most expensive fighter ever - has been plagued by a mysterious flaw that causes its pilots to become disoriented while at the controls from a lack of oxygen.
Pilots of the stealth fighter have complained that those oxygen-deficit problems have resulted in pilot dizziness, blackouts and other symptoms.
Martin reported that, according to the Air Force, there have been 22 unexplained cases over the past four years in which pilots experienced symptoms of oxygen deprivation.On Thursday, two Congress members who have been involved in the issue released information shedding more light on the problem, including a rate of hypoxia much higher than previously reported by the Air Force. New information also was released from a study done by Boeing on the issue and an internal survey of pilots, the majority of them who did not feel confident in the F-22's breathing system:
- Through May 31, 2012, the Air Force reported 26.43 hypoxia or hypoxia-like incidents among F-22 pilots per 100,000 flight hours - a rate that is at least 10 times higher than any other USAF aircraft. As recently as news coverage this week, the USAF continued to maintain that F-22 hypoxia rates "remain relatively low:"
- An early 2011 USAF aircrew survey found that "a majority of F-22 pilots surveyed did not feel confident" with the F-22 oxygen system, and USAF ordered the installation of C2A1 charcoal filters before returning the F-22 to full operations in September 2011.
- Tests performed by The Boeing Corp this spring found that the C2A1 filter "negatively impact[ed] thebreathing system" for F-22 pilots, and increased breathing resistance outside of acceptable standards. Boeing formally recommended discontinuing use of the filters on April 2nd - a recommendation that ultimately was adopted by the Air Force.
In a May 10 letter, Sen. Mark R. Warner (D-VA) and U.S. Rep. Adam Kinzinger (R-IL) recommended that USAF tap the expertise of the U.S. Navy, NASA and others to help identify and correct these recurring F-22 issues.
Sen. Warner and Rep. Kinzinger also repeated their call Thursday for the USAF and the Virginia Air National Guard to rescind reprimands and other disciplinary proceedings initiated against Capt. Wilson and Maj. Gordon after they stepped forward under The Military Whistleblower Protection Act.
"I am troubled that two brave pilots had to risk their careers and two relatively new members of Congress had to apply pressure to force the Air Force to move off-the-dime on this," Sen. Warner said. "The safety of these pilots and the communities over which they fly should be everyone's paramount concern. The F-22 program has cost $80 billion so far, but the most expensive fighter jet in the world is useless if we can't ensure the safety of the pilots who fly it."
The F-22 was grounded last year while engineers searched for something that could be contaminating the cockpit air, but the Air Force returned it to flight, sending the F-22s to the Persian Gulf, without finding the cause.
Now, investigators are zeroing in on a part of the flight suit called the "Combat Edge," which "hampers breathing and causes oxygen loss when combined with a physiological condition that collapses air sacs in the lungs," CNN reports.
The Air Force report is also expected to state that another possible problem for pilots is a condition called acceleration atelectasis, which causes a pilot's lungs to not effectively deliver oxygen to the bloodstream. The extreme effects of g-forces along with the pure oxygen breathed by pilots could lead to the condition.
Following the "60 Minutes" report, Secretary of Defense Leon Panetta limited the flights of the F-22 fighter jet to regions where pilots can quickly land the plane if they experience oxygen problems, and also ordered the investigation into the oxygen deprivation problem. The report detailed above is just the first of the monthly updates expected from the Air Force on the problem.
Watch the full "60 Minutes" report below