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​An F-35B Lightning II from Marine Fighter Attack Squadron 121 takes off from MCAS Yuma, Ariz., launching the squadron's first orientation flight, Feb. 21, 2013. The Marine Corps grounded its Yuma-based strike fighters on June 22, 2017, due to problems with the jet's logistics systems. USMC photo by Cpl. Bill Waterstreet.

​—Brian Everstine

The Marine Corps on Thursday temporarily suspended F-35 flight operations at its Arizona base due to concerns with the jet's logistics systems as USAF investigators continue efforts to find the root cause of hypoxia-like incidents in its variant.

USMC officials grounded their jets at MCAS Yuma on Thursday, saying the move is "very temporary," according to Inside Defense. The Air Force said Thursday afternoon that it has no concerns about the F-35's Autonomic Logistics Information System and that its flight operations are normal outside of Luke AFB, Ariz.

F-35A flight operations remain limited at Luke as investigators try to figure out what caused the five physiological events that prompted a grounding of the base’s fleet for a little over a week.  Of those five cases, there has been no "common denominator" yet, Air Force spokesman Col. Patrick Ryder said Thursday. However, F-35s at Luke are ordered to stay under 25,000 feet—the altitude above which the five incidents occurred. Luke has also changed ground procedures to mitigate risks to pilots, expanded training to increase the understanding between pilots and medical communities, increased minimum levels for backup oxygen systems for each flight, and offered pilots the option of wearing sensors during flight.

In addition, Air Combat Command has mandated that all pilots report hypoxia-like incidents through operational channels, as opposed to medical reports. This allows the information to be shared "across the enterprise," Ryder said.

The F-35 Joint Program Office has convened a study consisting of engineers, medical specialists, Lockheed Martin officials, the Air Force Life Cycle Management Center, and other experts who are "all working together to look at that issue," Ryder said.

Air Force Chief of Staff Gen. David Goldfein said Wednesday it’s possible the metering system at a higher altitude might not accurately be metering the oxygen, according to the Washington Examiner. However, Ryder said Thursday there has not been a root cause identified and the study continues.