Air Force base halts flights of F-35s after pilots report 'hypoxia-like symptoms' There have been five reports of hypoxia-like symptoms at the base since May 2.

 -- Luke Air Force Base in Arizona halted flights of its F-35 fighter jets on Friday after an increase in the number of pilots experiencing "hypoxia-like symptoms."

Five pilots have reported the symptoms since May 2, leading the base to cancel flying operations and review the concerns with pilots, the Air Force said. In each of the five instances, the pilots were able to use the aircraft's back-up oxygen system and land safely.

Hypoxia is a deficiency in the amount of oxygen reaching the body's tissues.

"Wing officials will educate U.S. and international pilots today on the situation and increase their awareness of hypoxia symptoms," Capt. Mark Graff, Air Force spokesman, said in a statement on Friday. "Pilots will also be briefed on all the incidents that have occurred and the successful actions taken by the pilots to safely recover their aircraft.

He continued: "Flight medicine will brief physiological event symptoms and also the extensive measures that are being taken to analyze data collected from the incidents."

The base will also hold an open forum for pilots to discuss concerns, he added.

No other bases with F-35 aircraft canceled operations on Friday. An Air Combat Command spokesperson told ABC News that a similar trend has not been seen with F-35 pilots on other bases.

Recently, the Navy has experienced hypoxia-related issues with its T-45 training jet. Flights of that aircraft were grounded across three bases in April for about a week due to protests by pilots that the oxygen system wasn't functioning properly.