"We determined with confidence the source of the unexplained physiological incident resides in the F-22 cockpit," Lyon said.
The Air Force has been investigating why a number of F-22 pilots have experienced a mysterious loss of oxygen while in the air, causing dizziness and confusion known as hypoxia, since spring 2011. Oxygen problems that have caused hypoxia-like symptoms in pilots and ground crew members have occurred for the past four years.
In recent months, Air Force officials, under pressure from Congress and Secretary of Defense Leon Panetta, have searched for a root cause of the problem and have thoroughly examined the system as a whole and found what they believes is the cause.
"In the end there is no smoking gun," Lyon told reporters at the Pentagon Tuesday during a briefing laying out the details of the findings.
The Air Force found four main components to the cause of the problem:
-- The upper pressure garment, or vest, that the pilots were wearing
-- The oxygen-delivery hoses on the vest
-- The valve in the quick connection point in those hoses
-- An air filter on the hoses designed to filter out chemical and biological agents
The Air Force had checked each of those parts of the system independently and they all worked as expected. But only once had the service checked the entire system together.
"There was a rudimentary testing that was done on the vest and it said that it inflates early and that it impedes the mobility of the pilot in the cockpit, and that was it. They didn't study the long term physiological impact of having this inflated," Lyon said.
After that rudimentary test was done, the entire F-22 fleet was grounded, but is now flying with limits on how high the planes can fly and how far from a safe landing strip they can go.
Some critics had blamed the dangerous chemicals on the plane's exterior that help make it stealthy to enemy radar, but the Air Force ruled that out.
"How did we eliminate contamination as the root cause? We did this through months of exhaustive testing on flight tests and line operational aircraft. We poured over aircraft involved in incidents. We analyzed thousands of samples of gases, volatile and semi-volatile compounds, solids, liquids and particulate matter. We compared these samples to occupational hazard standards and we checked the levels in incident aircraft and pilots against non-incident aircraft and pilots -- we found nothing remarkable," Lyon said.
Blaming the vest and the attachments doesn't answer why six ground maintenance crew members, who don't wear the vest, complained of hypoxia-like symptoms, including dizziness and lightheadedness.
Lyon blamed hunger and thirst.
"If you haven't eaten normally or you haven't fully hydrated, those type of things can begin degrade your personal performance," Lyon said. "These folks had some of these symptoms, which are ambiguous for other things that could happen to them so they reported based on that so there's a chance their diet wasn't right that day, they didn't have the hydration level that they needed."
Lyon also said some of them may have been sickened by exhaust from the jets they were working on.
As for the F-22's future, the hoses, filters and vests will be redesigned before the F-22 returns to fully operational status.
But Lyon warned that the problem will never be entirely solved. "There will be physiological incidents in the future in the F-22 and other aircraft -- that goes with the territory of high performance fighter aircraft and flight operations."
