For years now, Lockheed and the Air Force have been trying to figure out what was causing F-22 pilots to lose oxygen, and now they've finally hit on it, and it turns out, it's not a part of the plane. Apparently a valve in an inflatable vest pilots wear to help them breathe during high-altitude flight was making it inflate when it shouldn't have, Pentagon spokesman George Little told reporters on Monday. So to fix the problem, the Air Force will simply replace the valves and remove a filter they'd installed in cockpits to find contaminants.

Now the planes, which have never flown in combat, are finally getting deployed to Kadena Air Force Base in Japan. Secretary of Defense Leon Panetta said on Monday he had eased flight restrictions he'd placed on the planes in May, as the Air Force was confident they'd solved the problem. But oh, what a headache it's been trying to figure out what was wrong. The safety concerns led to a fleet-wide grounding last year, and in May Lockheed got a $19 million contract to replace the planes' oxygen system. In May, two pilots came forward as whistleblowers to tell 60 Minutes they felt afraid for their lives when flying the planes. That's when Panetta ordered a fleet-wide survey of all pilots, and subsequently ordered them to fly close to the ground and within easy access of an air field. As recently as this month, the Air Force was saying it was stumped by the problem.

Of all the reports on Monday's announcement, Spencer Ackerman's in Wired's Danger Room was the only one we saw that addressed the question of why the discovery took so long, quoting Gen. Norton Schwartz, the retiring Air Force chief of staff as saying, "This is a unique aircraft… There were aspects of this, from the physiological point of view of the aviator, [that] weren’t well-enough understood." Now we know and pilots can breathe a whole lot easier.