The FAA said the airline brought two MD-83 aircraft back into service in December 2007 and flew them 58 times in violation of regulations.

Pilots had reported problems with the planes. But the airline "used the wrong provisions of its Minimum Equipment List" when returning the planes to the active fleet, the FAA said in a statement.

Using one the planes landed the airline with $4.1 million in civil penalties.

The plane was flown Dec. 11-12 after maintenance on its autopilot system "was improperly deferred," the FAA said.

That aircraft could have flown under limitations, but it was flown in airspace where it should not have been, the statement said.

After an FAA inspector pointed out the deferred maintenance issue, the American kept the plane in service, flying it 10 more times before the problem was fixed, the FAA said.

The plane flew 36 more times in passenger-carrying flights after the autopilot disconnected during a landing on Dec. 21, FAA said. "Airline maintenance later discovered the fault was in a radio altimeter – not the autopilot," the statement said.