FAA probe into Southwest Airlines' aircraft maintenance

The largest carrier at Long Island MacArthur Airport is being investigated over how it performed maintenance on aging aircraft, according to the Federal Aviation Administration.

FAA investigators are probing Southwest Airlines and a contractor for allegedly performing aircraft maintenance without agency-approved methods, said Lynn Lunsford, an FAA spokesman in Fort Worth.

"We're conducting an investigation of some past maintenance issues at Southwest," Lunsford said Tuesday.

Failure to follow maintenance procedures could risk safety because the maintenance work is designed to identify and prevent metal fatigue. Jets can develop tiny cracks in surface metal, especially in stressed areas, such as around windows. Patches are used to shore up weak spots, and the fix chosen by Southwest was new aluminum skin.

The work done by Aviation Technical Services, of Everett, Wash., wasn't approved by FAA inspectors, and may have actually caused more cracks in the jets' fuselage because the airframes weren't properly braced when old rivets and sheet metal were replaced, according to a source familiar with the FAA's probe.

Brad Hawkins, a spokesman for Southwest, said the airline recognized the FAA's "authority as a regulatory body" and was cooperating with the investigators.

"Above all else, the primary focus at Southwest Airlines is safety," Hawkins said in a statement. "All of our maintenance operations promote aviation safety by working in coordination with the FAA, equipment manufacturers and aircraft maintenance organizations to make every effort to ensure that our fleet is maintained in accordance with applicable regulations and is aligned with best practice in the industry."

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A source familiar with the FAA's investigation said the probe centers on 44 Boeing 737 aircraft that have routinely flown various routes across the nation, totaling 100,000 miles. The source wasn't authorized to speak about the investigation because it is still continuing.

Southwest could face fines, perhaps in the millions, from the FAA if the maintenance lapses are upheld. The letter outlying the FAA's directive for dealing with metal fatigue on older Boeing 737s was dated April 2009, the source said.

FAA inspectors discovered the problems with Southwest's maintenance work in September, the source said.

Last year, the FAA found a Southwest subcontractor installed parts that weren't approved by FAA on 82 planes. The agency gave Southwest four months to replace the parts, and Southwest stopped using the subcontractor that did the work. No fine was issued.

But the FAA has also become more aggressive about fining airlines it accuses of violating safety orders.