Meanwhile, Robert Gless, deputy director of the Air Transport Division of the Transport Workers Union of America, dismissed the notion that the problems with loose seats were linked to labor issues as "without any basis in fact."

Seat installation work is largely carried out by outside contractors, rather than maintenance personnel employed by the airline, he said in a statement.

"Problems related to seats are less likely a labor problem, but rather a management issue related to outsourcing work to third-party facilities," he said.

American Airlines plans to increase its use of outside maintenance facilities, including in China and other overseas locations, as it seeks to exit bankruptcy, he added.