About 40 of the US Air Force’s Lockheed Martin F-22A Raptors have returned to flight status at Joint Base Elmendorf-Richardson (JBER) in Alaska following a new, four-day grounding event.

But 30 more F-22As remain parked at another base as concerns linger over mysterious life support system problems that have sometimes proved a critical risk to pilots for more than two years.

JBER confirms all 40 F-22As based in Alaska were cleared by local commanders to resume flying on 24 October. Its Raptors had been grounded since 20 October in a “temporary pause” triggered by reports of life support system problems at Langley AFB, Virginia.

About 30 F-22As at Langley remain grounded as base officials continue to investigate the source of the latest life support system malfunction, which reportedly left one pilot light-headed.

Flight operations for the F-22A fleet are made at the discretion of base commanders. So far, only the JBER F-22As were grounded as a result of the incident at Langley. The US Air Combat Command confirms that no other aircraft besides Langley’s are stood-down for safety reasons.

Meanwhile, a panel led by retired General Greg Martin is continuing to assess the safety of life support systems, including onboard oxygen generation systems (OBOGS), for several USAF combat aircraft types, including the F-22A and Lockheed F-35A. Martin’s panel is scheduled to release a public version of their assessment in November, according to the USAF.

Earlier this year, the air force grounded all its F-22As for four months to investigate several reports of pilots suffering from hypoxia-like symptoms. An intensive investigation failed to identify the source of the problems, or even replicate the conditions experienced by pilots on some missions.

The USAF returned the fleet to flight status on 21 September, but imposed a new set of safety procedures and continued monitoring of pilots’ health.

The F-22A fleet has flown more than 1,300 missions since the return to flight order was approved about one month ago.

Source: Flight International