American Airlines officially grounded 47 of its fleet of 102 Boeing 757s last Thursday for faulty cabin seats. Earlier in the week, American said the carrier believed it had identified faulty clamps as the cause of seats breaking loose on as many as six of its 757s, some in flight.

The first broken-seat incident occurred aboard a 757 on departure from Vail, Colo., on September 26. Then, after announcing that it had inspected 47 of the company’s fleet of one hundred and two 757s that seemed to use similar locking mechanisms, the airline announced the grounding so it could reinspect the fleet when additional seat problems appeared.

No one has been injured in any of these incidents as flight attendants moved affected passengers in flight to other locations in the cabin.

American now says an additional safety clamp will be required to ensure the seats remain in place. Reports identified AA maintenance subcontractor Timco as one of the groups that had initially worked on the aircraft in question. The airline was quick to express support for all external maintenance subcontractors. In a statement, the Transport Workers Union representing mechanics at American said, “Problems related to seats are less likely a labor problem, but rather a management issue related to outsourcing work to third-party facilities.”

American Airlines, currently operating under Chapter 11 bankruptcy rules, operates one of the oldest aircraft fleets of any U.S. legacy carrier.