The U.S. Air Force has indefinitely barred the Boeing-built KC-46 from carrying cargo and passengers, the trade publication Defense News reported Wednesday.

The decision followed an incident in which the cargo locks on the bottom of the floor of the aircraft became unlocked during a recent flight, creating concerns that airmen could potentially be hurt or even killed by heavy equipment that suddenly bursts free during a flight, Defense One reported.

An Air Force spokesman said that “until we find a viable solution with Boeing to remedy this problem, we can’t jeopardize the safety of our aircrew and this aircraft.” The Air Force issued a Category 1 deficiency report on the problem, signifying a serious technical issue that could endanger the aircrew and aircraft or have other major effects, Defense One reported.

Boeing’s KC-46 tanker has been plagued by delays and problems, ranging from cost over-runs to loose debris found inside completed planes. The Air Force took the first tanker in January only after working out an agreement with Boeing that it will fix certain flaws in the aircraft’s refueling systems over the next three to four years, and that until those fixes are implemented the Air Force will withhold up to $28 million from the final payment on each aircraft.

Boeing said it’s aware of the latest issue and is working to resolve it, Defense One reported.