The US Air Force’s (USAF) advanced stealth fighter jet, F-22 Raptor, will soon resume operations after being grounded for four months over safety concerns regarding the aircraft’s oxygen system, air force chief of staff General Norton Schwartz has said.

The entire fleet will undergo a thorough inspection of the life support systems with follow-on daily inspections, while pilots will undergo baseline physiological tests and use additional protective equipment.

The return-to-fly process will start with the instructor pilots and flight leads gaining proficiency in flying the aircraft, followed by other F-22 wingmen.

“We now have enough insight from recent studies and investigations that a return to flight is prudent and appropriate,” Schwartz added.

The radar-evading F-22 Raptors have been barred from flying above 25,000ft since January following the crash of a jet in Alaska during a training flight.

Currently, the USAF has fielded 170 F-22 Raptors in its fleet and has plans to build a total of 187 jets.