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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 already had 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 air and maintenance crews.

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 jet 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.