Federal officials are investigating Southwest Airlines over the way it handled structural repairs on dozens of jets, according to a person familiar with the situation.
The Federal Aviation Administration confirmed Tuesday that it is investigating whether Southwest followed safety orders dealing with the maintenance of older planes.
Inspectors believe Southwest and a repair shop near Seattle conducted body repairs on 44 jets without getting FAA approval first. The jets were then used on more than 100,000 flights, said the person familiar with the situation, who spoke on condition of anonymity because details of the investigation are not public.
The investigation centers on the way Southwest and a company it hired, Aviation Technical Services, or ATS, worked on the fuselages of Boeing 737 jets.
As they age, jets often develop tiny cracks especially in stressed areas such as around windows. Patches are often used to shore up weak spots. According to the person familiar with the situation, Southwest and ATS decided to replace the patches on some planes with new aluminum skin.
Southwest and ATS got Boeing's approval, but didn't ask the FAA about it. Inspectors believe the mechanics might not have adequately reinforced the aircraft frame while installing new skin panels, the person said. However, the FAA granted retroactive approval to the work.
Southwest spokesman Brad Hawkins said the airline works with the FAA, manufacturers and maintenance operators "to make every effort to ensure that our fleet is maintained in accordance with applicable regulations" and the best safety practices of the industry.
ATS officials did not immediately respond to phone messages.
The investigation is being handled by FAA officials in Seattle and a decision whether to seek a fine against Southwest could be weeks or months away.
In a similar case last year, the FAA found that a Southwest subcontractor installed parts that weren't approved by FAA on about 80 jets. Rather than fine the airline, the FAA gave Southwest four months to replace the parts, and Southwest stopped using the subcontractor that did the work.
But the FAA has also turned more aggressive about fining airlines that it accuses of violating safety orders.
Last year, Southwest agreed to pay $7.5 million to settle charges that it operated nearly 60,000 flights with planes that had missed mandatory inspections for structural cracks.