The U.S. Air Force on Wednesday cleared its F-22 Raptor fleet to return to service following a four-month grounding over concerns that the jets' pilots weren't getting proper oxygen.
Bases are cleared to start flying the fighter jets under a "return to flight" plan - with new rules including daily inspections of the life-support systems - that the Air Force announced earlier in the week,Â said Staff Sgt. Heidi Davis, spokeswoman for the Air Force's Air Combat Command.
The command grounded the jets on May 3 during an investigation into reports that 12 pilots had experienced "hypoxia-like symptoms" aboard the F-22 since April 2008. Hypoxia is oxygen deficiency.
Air Force panels still are investigating the reports and the jets' oxygen generation systems, and a report on the systems is expected to be released in the fall. Air Force spokesman Lt. Col. John Haynes said that with the study still happening, he couldn't comment on any findings.
However, the serviceÂ is using some of what it has learned to make "changes to the (onboard oxygen generation systems) and other life support systems elements to increase our safety margin," Haynes said.
"We've also identified areas where education, training and equipment modifications will increase the safety margin for air and ground crews," Haynes said.
The fleet's life support systems will be inspected extensively before they're allowed to fly, and daily inspections will follow, the Air Force news service reported Monday.
"We now have enough insight from recent studies and investigations that a return to flight is prudent and appropriate," Gen. Norton Schwartz, Air Force chief of staff, said in the Air Force news report. "We're managing the risks with our air crews, and we're continuing to study the F-22's oxygen systems and collect data to improve it's performance."
The Air Force says that as of May, it had deployed 170 of the jets since the F-22 entered service in 2005.
The jets' return to flight will be gradual, with some pilots needing to prove their proficiency after the four-month grounding, Davis said. Not all bases with F-22s necessarily will resume flying the jets on Wednesday; the decisions will be made locally and will depend on what they have to do to get the jets ready, according to Davis.