F-35 flights grounded at Arizona base because of health concerns

June 10 (UPI) -- The U.S. Air Force temporarily grounded all F-35 jets flying at an airbase in Arizona after pilots reported oxygen deprivation in five incidents.

Flights of the 55 F-35A Lightning II jets were halted for one day at Luke Air Fore Base in Glendale, the Air Force said in a release Friday.

Operations at five other U.S. bases with F-35 jets are not affected and the suburban Phoenix base planned to resume flights Saturday.

Since May 2, five pilots' symptoms had a variety of symptoms that ranged from dizziness and disorientation to tingling in their extremities when the main oxygen unit malfunctions, said Maj. Rebecca Heyse, a chief public affairs officer for Luke, said to AZCentral.

In each case, the backup oxygen system worked and the pilot safely landed the plane.

Air Force spokesman Capt. Mark Graff said to CNN the grounding was taken "not out of fear or out of danger, but out of an abundance of caution."

"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 at Luke, in a statement. "We are taking the necessary steps to find the root cause of these incidents."

Wing officials educated U.S. and international pilots on the situation.

In 2011, F-22 Raptor pilots frequently complained about hypoxia-like symptoms during flights. They were grounded for five months until the Air Force discovered the cause was defective oxygen-delivery components in the pilot's vest.

Lockheed Martin manufactures the F-35A fighter jets and they declared them combat ready for the Air Force last year.

The F-35B is the Marine Corps version of the Joint Striker Fighter and it was declared combat ready in 2015. The F-35C Nary version is scheduled to be combat operational next year.