The Southwest fine was for 60,000 flights involving planes that had missed required examinations for structural cracks. That case settled for $7.5 million a year later.
The FAA itself is coming under criticism by a government watchdog for lax oversight of American's aircraft maintenance.
Loose fastening led to wire damage in several dozen of American's 290 MD-80s and, in at least a few cases, an electrical discharge that's a potential fire threat, according to the government and industry officials. They asked not to be identified because they weren't authorized to speak publicly about the two-year investigation.
The airline and officials with its mechanics union said its MD-80s never had that second type of problem, known as electrical arcing, and long has contended that safety never was jeopardized.
The FAA ordered hundreds of MD-80s grounded in April 2008 for safety inspections, disrupting travel for thousands of passengers.
FAA spokesman Lynn Lunsford said it would be premature to comment on any possible fine against American because the investigation was not finished.
American spokesman Tim Wagner said the airline wasn't aware of any pending fine. He also said in an e-mail that the airline "found no evidence of any chaffing of wires in its inspection and reworking of the wire bundles."
American found only two planes where the protective wire covering "had some evidence of rubbing," but the wires in those bundle had no signs of chaffing.
A separate audit by the Transportation Department's independent watchdog involves allegations of maintenance problems, including landing gear that wasn't retracting properly and windshield heating systems that had electrical problems.
A spokesman for the Allied Pilots Association, which represents pilots at American, said the union brought some of the safety issues to the attention of the inspector general in 2008 after FAA inspectors failed to respond to the union's complaints. The FAA is part of the Transportation Department.
"We had been trying to bring some of these systematic issues to the attention of the FAA and were finding some significant push-back," said Sam Mayer, a spokesman for the union.
The FAA has submitted replies to be included in the audit that agree with many of the conclusions about maintenance problems at American and some of the findings about weak oversight.
Those problems were largely corrected during a special in-depth FAA review of American maintenance programs last spring, according to an FAA official who spoke on condition of anonymity because the audit hasn't been released.
Wagner said American has cooperated with the audit. He declined further comment.
In 2008, the FAA proposed a $7.1 million fine against American for violations that including flying two jets 58 times without making repairs after an FAA inspector and American's own mechanics found problems with their autopilot systems. Those problems were unrelated to the issues that led to the groundings.
