The U.S. Air Force has lifted a temporary altitude restriction that required Lockheed Martin [LMT] F-35A Lightning IIs at Luke Air Force Base in Arizona to fly below 25,000 feet.
The altitude limit, which ended Aug. 30, was imposed at the training base June 20 after five pilots experienced oxygen deprivation-like symptoms above 25,000 feet in May and early June. The Air Force said that while it has not identified the cause of the symptoms, it has taken steps to minimize labored breathing and carbon monoxide ingestion.
The new steps include requiring pilots to put on their oxygen masks when they step into the fighter jet’s cockpit to ensure they breathe clean air. Pilots also are receiving more training on recognizing and responding to oxygen-deprivation symptoms.
“We have great confidence in the F-35A and the ability and training of our pilots,” said Brig. Gen. Brook Leonard, commander of Luke’s 56th Fighter Wing. “We will continue to closely monitor operations and work with the [Defense Department’s F-35] Joint Program Office and the [Air Force’s 711th] Human Performance Wing on future improvements as we move forward building the future of air power.”
The Air Force said it collected data on heat and chemicals on the Luke flight line and found no evidence that pilots are exposed to excessive amounts when they walk to their jets.
Before imposing the altitude restriction, the Air Force grounded its F-35A fleet at Luke for almost two weeks.