Even the smallest mistake – or three of them – can translate into huge fines for airline companies. Southwest Airlines could be paying a $12 million fine to the Federal Aviation Administration because of allegedly improper repairs to its aircraft going back as far as 2006.

The Chicago Tribune reports that FAA investigators found three separate incidents in which Southwest and its hired contractor improperly repaired aircraft.

The incidents began in 2006 when Southwest carried out “extreme makeover” alterations to eliminate possible cracking of the aluminum skin on 44 Boeing 737 jetliners.

According to the FAA’s investigation, the contractor hired by Southwest – Aviation Technical Services –failed to follow required procedures regarding the placement of the airplanes on jacks and stabilizing them while replacing the fuselage skins on the aircraft. By not following the proper protocol, the airframe could shift and lead to problems with the new skin.

Despite begin notified of the issue, Southwest returned the jetliners to service and operated them when they were not in compliance with federal aviation regulations, the FAA says in a news release.

However, the agency later approved the repairs after the airline provided proper documentation that the repairs met safety standards.

The second incident occurred when the contractor applied sealant beneath the new skin panels but failed to install fasteners to all the rivet holes while the sealant was effective. The omission could have resulted in gaps between the skin and the plane’s surface which could let moisture inside leading to corrosion.

In the final case, the FAA alleges that Southwest failed to properly install a ground wire on water drain masts on two of its aircraft as required by the FAA Airworthiness Directive regarding lightning strikes. The airplanes were each operated on more than 20 passenger flights after Southwest Airlines became aware of the discrepancies but before the airline corrected the problem.

“The FAA views maintenance very seriously, and it will not hesitate to take action against companies that fail to follow regulations,” FAA Administrator Michael Huerta says in a news release.

A spokesperson for Southwest Airlines tells the Tribune that the incidents concern repair issues addressed several years ago, and that none of the allegations affect aircraft currently in operation.

“Southwest is committed to continuously making enhancements to our internal procedures, as well as improvements related to oversight of our repair vendors,” she says.

The airline has 30 days to respond to the FAA’s penalty letter.

FAA suggests $12 million fine for Southwest Airlines over repairs [The Chicago Tribune]

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