Here is a story about aircraft maintained by US mechanics. The MD-80's are all maintained in Tulsa
By ANDY PASZTOR
AMR Corp.'s American Airlines operated jets later found to have substandard repairs, and federal regulators are probing allegations that at least one plane was considered unsafe to fly at normal cruise altitude, according to people familiar with the matter.
The Federal Aviation Administration's latest moves, these people said, indicate the agency is expanding its probe into suspected structural problems with rear bulkheads on a small portion of American's fleet of McDonnell Douglas MD-80 jets.
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Associated Press Earlier this year, American took more than a dozen planes out of service.
Earlier this year, American took more than a dozen planes out of passenger service, retiring several of them, after finding they had improper bulkhead repairs. FAA inspectors are pursuing allegations from pilots that one of those MD-80s was believed to be in such poor condition that it was ferried without passengers from Dallas to the carrier's Tulsa, Okla., maintenance base at unusually low altitudes to avoid the stress of pressurizing the fuselage during the trip.
Preliminary FAA findings have identified as many as 16 American Airlines twin-engine MD-80s that were operated for months despite allegedly substandard bulkhead repairs. Agency investigators are delving into whether other MD-80s also may have been flown for repairs at low altitudes without passengers, these people said.
FAA officials have confirmed the investigation, though the agency hasn't divulged specifics.
American Airlines spokesman Tim Wagner said the carrier has responded to the agency's formal "letter of investigation," but also declined to comment on specifics. Mr. Wagner added that any actions or precautions taken earlier this year "whether airplane movements or repairs, were done with the highest level of safety in mind."
The rear bulkheads, located near the tail cone behind the last row of seats, are key structural parts than can cause rapid and dangerous cabin decompression if they rupture. No such structural failures on American MD-80s have been reported to the FAA.
Nonetheless, people familiar with the investigation said American potentially faces millions of dollars in civil penalties stemming from the widening investigation, and the FAA is also considering the unusual tactic of eventually taking punitive action against individual mechanics or supervisors who may have signed off on substandard work.
FAA inspectors previously suspected that one of the MD-80s requiring extensive structural repairs was abruptly retired to get it out of sight of government inspectors, according to people familiar with the matter. American has said those allegations "misrepresent the facts." That issue remains under investigation.
The widening probe comes at a time when American already faces possibly hefty FAA civil penalties for unrelated wiring maintenance slip-ups that forced the airline to briefly ground its entire fleet of MD-80s in the spring of 2008. Some estimates peg those potential penalties between $15 million and perhaps more than $50 million, but the agency hasn't disclosed its intentions.
According to people familiar with the carrier's legal strategy, American is likely to argue that special precautions to ferry planes for maintenance don't mean aircraft were unsafe to carry passengers. American, which is gradually replacing its MD-80 fleet with more fuel-efficient models, quickly retired at least five of the planes after finding improper bulkhead repairs.
How can a US airline offset costs and maintain their aircraft in the US? 
