Sen. John McCain said he was "concerned" after reports that the Marine Corps' version of the F-35 joint strike fighter was temporarily grounded Thursday, the second problem the tri-service aircraft has faced this month.

Flight operations were suspended at Marine Corps Air Station Yuma in Arizona for Marine Fighter Attack Squadron 211 over concerns with the plane's software backbone, after "anomalies" were found following an upgrade.

"I was concerned to learn that the Marine Corps has suspended F-35B operations at MCAS Yuma due to problems with the aircraft's Autonomic Logistics Information System. I am in close communication with the Marine Corps and Joint Program Office as they work to identify the root cause of these issues and resolve them as quickly as possible," McCain said.

The grounding comes just two days after Air Force F-35s at Luke Air Force Base in Arizona returned to flight after an 11-day pause due to concerns over the aircraft's onboard oxygen system. The problems occurred in May and early June, and investigators have yet to find the underlying cause of the oxygen issue. F-35 pilots at Luke now fly with altitude restrictions.

The F-35 is the most expensive weapons program in history, and involves variants for the Air Force, Navy and Marine Corps. The groundings have affected only the aircraft at those two Arizona bases.