(AP) KADENA AIR BASE, Japan -- Years before F-22 pilots began getting dizzy in the cockpit, before one struggled to breathe as he tried to pull out of a fatal crash, before two more went on television to say the plane was so unsafe they refused to fly it, a small circle of U.S. Air Force experts knew something was wrong with the prized stealth fighter jet.
Coughing among pilots and fears that contaminants were leaking into their breathing apparatus led the experts to suspect flaws in the oxygen-supply system of the F-22 Raptor, especially in extreme high-altitude conditions in which the $190 million aircraft is without equal. They formed a working group a decade ago to deal with the problem, creating an informal but unique brain trust.
Internal documents and emails obtained by The Associated Press show they proposed a range of solutions by 2005, including adjustments to the flow of oxygen into pilot's masks. But that key recommendation was rejected by military officials reluctant to add costs to a program that was already well over budget.
"This initiative has not been funded,'' read the minutes of their final meeting in 2007.
Minutes of the working group's meetings, PowerPoint presentations and emails among its members reveal a missed opportunity for the Air Force to improve pilot safety in the 187-plane F-22 fleet before a series of high-profile problems damaged the image of an aircraft that was already being assailed in Congress as too costly. Its production was halted last spring and the aircraft has never been used in combat.
Among the problems reported after the working group's warnings:
In 2008, pilots began reporting a sharp increase in hypoxia-like problems, forcing the Air Force to finally acknowledge concerns about the F-22's oxygen supply system.
Two years later, the oxygen system contributed to a fatal crash. Though pilot error ultimately was deemed to be the cause, the fleet was grounded for four months in 2011. New restrictions were imposed in May, after two F-22 pilots went on the CBS program "60 Minutes'' to express their continued misgivings.
The Air Force says the F-22 is safe to fly a dozen of the jets began a six-month deployment to Japan in July but flight restrictions that remain in place will keep it out of the high-altitude situations where pilots' breathing is under the most stress.
One of the working group's proposed fixes, a backup oxygen system, is expected to be in place by the end of the year. And the Air Force, which blamed the oxygen shortage on a faulty valve in the pilots' vests, says a fix to that problem is also in the works. The working group also proposed changes in warning systems to alert pilots to system failures and urged enhanced tracking of potential health hazards to pilots and ground crew caused by the materials used to bolster the aircraft's stealth two more issues the Air Force investigations would later focus on.
More broadly, the Air Force now concedes that, while its own experts were tackling the F-22's issues, it was too aggressive in cutting back on life-support programs intended to ensure pilots' safety. It is now in the process of rebuilding them.
The F-22's gradual return to regular flight operations follows an exhaustive investigation over the past year by the Air Force, NASA, experts from Lockheed Martin, which produces the aircraft, and other industry officials.
But the documents obtained by AP show many of the concerns raised in that investigation had already been outlined by the working group that was formed in 2002, when the fighter was still in its early production and delivery stage.
It called itself RAW-G, for Raptor Aeromedical Working Group, and brought together dozens of experts in life support, avionics, physiology and systems safety, along with F-22 aircrew and maintainers.
The group was founded by members of the F-22 community who were concerned about how the unique demands of the aircraft could affect pilots. The fighter can evade radar and fly faster than sound without using afterburners, capabilities unmatched by any other country. It also flies higher than its predecessors and has a self-contained oxygen generation system to protect pilots from chemical or biological attack.
According to the Air Force, RAW-G was created at the suggestion of Daniel Wyman, then a flight surgeon on Florida's Tyndall Air Force Base, where the first F-22 squadron was being deployed. Wyman is now a brigadier general and the Air Combat Command surgeon general.
By the time RAW-G got going, some pilots were already experiencing a problem called "Raptor cough'' fits of chest pain and coughing dating back to 2000 that stem from the collapse of overworked air sacs in the lungs.
The group concluded that the F-22's On-Board Oxygen Generation System or OBOGS was giving pilots too much oxygen, causing the coughing. The more often and higher the pilots flew after being oxygen-saturated, group members believed, the more vulnerable pilots affected by the condition would be to other physiological incidents.
RAW-G recommended more tests and that the F-22's oxygen delivery system be adjusted through a digital controller and a software upgrade.