Lyon said the rate was clearly too high, but also noted that there had been no incidents reported since March 8, and the Air Force was getting closer to resolving the issue.

“I expect that by the end of the summer we will have identified all the significant and major contributors, and that a number of months after that we’re going to get back to normal operations,” Lyon, a fighter pilot with more than 3,800 hours of flight time, told Reuters late on Thursday.

“But I don’t want to oversell what we’ve learned. We know it’s significant. We know it’s contributory, but we’re not ready to say ‘we’ve found the smoking gun’.”

“PLANNING FIXES”

Lyon said he had briefed Air Force leaders, senior officers from the Joint Staff, Pentagon officials and lawmakers this week about the work of a joint military-industry task force he has led since January.

He said the Air Force was already planning several fixes to address the oxygen deprivation issue, including a redesign of the pressure garment and moves to widen the hoses that deliver oxygen to pilots in the cockpit, even as research continued.

Lyon said he could not estimate the cost of redesigning the equipment, but said he did not expect it to be too high since none of the anticipated fixes was a major engineering challenge.

The general, who serves as director of operations for Air Combat Command, said the Air Force had evaluated the aircraft’s life support systems from end to end, finding some vulnerabilities at different points, mostly items that reduced the flow of oxygen to the pilot.

Senator Mark Warner, a Virginia Democrat, and Representative Adam Kinzinger, an Illinois Republican, said the Air Force data showed just over 26 incidents of oxygen deprivation per 100,000 flight hours on the F-22, a rate they said that was “at least 10 times higher than any other U.S. Air Force aircraft.”