American Airlines said Tuesday that an internal investigation has found improperly installed clamps were the "root cause" of passenger seats coming loose on airborne planes.
The results of the probe came after the airline acknowledged earlier in the day that seats came loose on a flight last week from Dallas-Fort Worth International Airport to Vail, Colo. Seats came loose aboard the same plane Monday and a second plane Saturday, according to the airline.
Airline spokeswoman Andrea Huguely said in a statement late Tuesday that the internal investigation focused on one of three types of main cabin seats on Boeing 757 planes and how the rows of the seats fit into the track that's used to secure the rows to the floor of the aircraft.
"Our maintenance and engineering teams have discovered that the root cause is a saddle clamp improperly installed on the foot of the row leg," the statement said. "The clamps were used on only 47 of our 102 Boeing 757 airplanes."
Huguely said 36 airplanes were evaluated overnight and 11 will be evaluated to finish the inspection. She added that the issue "does not seem to be tied to any one maintenance facility or one workgroup." The airline has notified the Federal Aviation Administration of the review's findings.
An American Airlines official told CBS News that of the 36 planes inspected so far, six were found to have a single row of seats that were not properly installed. That figure includes the two planes involved in the reported incidents. All of the aircraft cleared checks prior to takeoff, the official said.
Earlier, Huguely adamantly denied that the spate of loose-seat reports were the result of sabotage by workers. American's union employees are unhappy about pending layoffs and cuts in pay and benefits that American has imposed since filing for bankruptcy protection in November. American accuses some pilots of conducting an illegal work slowdown that has caused a jump in canceled and delayed flights.
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.
No further problems were noticed until a flight Monday from New York to Miami, which returned to Kennedy Airport. Another plane making a Boston-to-Miami trip on Saturday made an emergency landing in New York after a row of seats came loose in flight.
The seats on both planes had been removed and reinstalled during recent maintenance at an American Airlines maintenance base in Tulsa, Okla., and a Timco Aviation Services facility in North Carolina. In both cases American employees were the last to touch the seats, Huguely said.
A Timco spokesman declined to comment beyond saying that the company is still investigating.
The Federal Aviation Administration said it is looking into the incidents.