The Air Force has “temporarily” grounded a squadron of F-35s at Luke Air Force Base in Arizona because five pilots in the past five weeks have reported symptoms consistent with oxygen deprivation, known as “hypoxia,” the service announced on Friday.
In all five cases, the F-35’s back-up oxygen system was engaged and the single-seat planes landed safely.
“The Air Force takes these physiological incidents seriously, and our focus is on the safety and well-being of our pilots,” said Brig. Gen. Brook Leonard, 56th Fighter Wing commander in a statement. “We are taking the necessary steps to find the root cause of these incidents.”
The temporary grounding applies only to Luke Air Force base.
“Air Force senior leaders are aware of the incidents and are providing support and resources as necessary to protect pilots,” said Capt. Mark Graff, an Air Force spokesman at the Pentagon.
Graff said the Air Force has assembled a team of engineers, aircraft maintainers and aeromedical specialists to try to figure out what led to the hypoxia-like symptoms, and any findings will be shared with U.S. allies who have bought, and also operate the F-35A model.
The F-35 is built by Lockheed Martin and is the Pentagon’s most expensive weapons acquisition program ever, with a total cost of more than $1 trillion.
The latest production lot of the Air Force version of the plane has a price tag of $95 million a copy.
The Navy operates a version that can take off and land on aircraft carriers, while the Marine Corps variant can take off and land vertically.
