On Mar. 12, U.S. aviation regulators proposed a US$787,500 fine against American Airlines, a unit of AMR Corp, for allegedly flying aircraft not in compliance with maintenance requirements.

The incidents alleged by the Federal Aviation Administration (FAA) occurred in 2008 and 2009 and involved six planes, two of which were operated on commercial flights even though the company said it would not do so until outstanding work was completed.

American, which has 30 days to appeal the proposed penalty, said in a statement that it planned to discuss the matter with the FAA.

The agency has reduced penalties against airlines on appeal.

The FAA said that airline mechanics in April 2008 diagnosed problems with one of two air data computers on an MD-82 jetliner. That system is critical for calculating airspeed, altitude and other readings.

American improperly operated the plane on 10 flights before replacing the computer, the FAA said, adding that flight crews during that timeframe were "led to believe" that both computers were working properly.

In a second case, the FAA said it found that American allegedly failed to follow requirements for inspecting rudder components on four Boeing Co 757s in March 2008.

American promised to ground the planes until the work was completed but two days later operated two of the planes on three flights, the FAA said.

In a third incident, the FAA alleged that mechanics returned another MD-82 to service in May 2009 without completing a required maintenance checklist.

A follow-up inspection of the plane's tail section found loose screws and other problems.