Last month, American Airlines grounded dozens of Boeing 757 airliners after passenger seats came loose on four flights. Just a few weeks earlier, another American plane, a Boeing 767, was grounded after a problem was reported with the installation of some seats, though in that case no seats actually came loose.

American, like other carriers, is in the midst of reconfiguring its coach section to give more leg room to some economy seats. To get the extra space, it is creating three rows instead of four. The airline then charges more for the seats, which it calls Main Cabin Extra.

American Airlines hired outside contractors to install passenger seats with more leg room. The seats have come loose on several flights. And airline documents show that those workers did not understand how to properly install the seats.

Photo Credit: American took dozens of its Boeing 757s out of service when passenger seats loosened.