UNITED NEWS INTERNATIONAL (UNI) — The U.S. Air Force has grounded all B-1 bombers over safety concerns.

The service announced on June 8 that it had ordered a stand-down of its entire fleet of B-1B Lancer bombers due to unspecified concerns about the aircraft’s ejection seats.

Air Force spokesman Major William Russell said in a statement, “During the safety investigation process following an emergency landing of a B-1B in Midland, Texas, an issue with ejection seat components was discovered that necessitated the stand down.”

There is reportedly no timeline for when the bombers will be cleared to fly again.

The highly versatile B-1 is a major component of the U.S. long-range bombing fleet and carries the largest conventional payload of any aircraft in the Air Force.

The aircraft’s grounding comes as the Pentagon continues to deal with a series of aviation mishaps and crashes that has brought into question U.S military readiness.