The 173rd Fighter Wing at Kingsley Air Field in Oregon resumed flying its 30 F-15Cs March 29 after a week-long grounding.

Master Sgt. Jennifer Shirar, a spokeswoman for the 173rd, said in an email that the planes were grounded the evening of March 22 after a maintenance records review raised questions about whether one plane had been properly repaired five years ago.

The 173rd is an Oregon Air National Guard unit that trains F-15 pilots.

Shirar said that after the discrepancy was discovered, the wing had to verify its aircraft had been repaired properly and didn’t have structural issues that would put its flight crew at risk.

“Out of an abundance of caution, we stood down flying so that a team from the System Program Office could have the opportunity to assess the aircraft,” Shirar said. “Safety is always our number one priority.”

Shirar said an engineering and repair team from that office arrived at the base March 27, and its inspections were finished the following day.

The F-15 in question had a minor crack on a non-structural bracket, she said, but its longeron — a 12-foot aluminum beam that ties the F-15’s front and rear fuselage together — appeared to be structurally sound, and the wing resumed flying status.

All F-15s are flying, except for those undergoing routine maintenance, Shirar said.

The grounding was first reported by Military.com.