TULSA, Oklahoma - Forty-seven American Airlines 757s are being inspected after passengers' seats come loose in mid-air on three different flights. The latest flight was out of Dallas.

The same thing happened Monday on a flight from New York and over the weekend on a Boston plane.

The airline blames seat clamps that were installed improperly.

An airline spokesman reported the seats had been installed at Tulsa's maintenance base and in North Carolina at TIMCO - a private aircraft maintenance facility - but that the last people "to touch" the seats were American Airlines employees.

"We wish the company would have waited to gather all the facts before they started placing blame," said John Hewitt of the Transport Workers Union Local 514.

John Hewitt represents local union workers. He says TIMCO installed the seats.

And according to Hewitt, the planes flew onto Tulsa for other maintenance - not related to the seats. Hewitt and the unions are pointing the finger back at American for deciding to outsource the work.

"It's been accomplished here in Tulsa and you've never heard of this type of problem before, but now that they're outsourcing some of this type of work, now this problem rears its head," he said.

Maintenance workers from Tulsa were flown to New York to help inspect the fleet. Inspectors have found six planes so far with poorly-installed clamps. 

The problem planes were worked on by several crews in different cities. After seats came loose the first time, a crew in Vail tightened them and the plane made a return flight to Dallas. It flew to Boston later that day, where the seats were tightened again, according to American.

The Federal Aviation Administration said it is looking into the incidents.