Regulators at the Federal Aviation Administration want to hand down a $12 million fine to Southwest Airlines for insufficient repair work on dozens of aircraft.
The penalty relates to "extreme makeover" skin-sealing repairs on 44 Boeing 737s to prevent aluminium cracking on the planes’ hulls which was carried out by contractor Aviation Technical Services under the supervision of Southwest.
The FAA said the contractor did not comply with standard procedures for replacing the skins.
Southwest flew the airplanes for a period when the repair work did not meet standards and even after "the airline was put on notice that these aircraft were not in compliance," the agency said.
"Having fully resolved the repair issues some time ago, none of the items raised in the FAA letter affect aircraft currently being operated by Southwest Airlines," said Southwest spokeswoman Brandy King.
The carrier has one month to reply to the allegations.
Southwest was involved in a similar case in 2008 with the FAA when it operated around 60,000 flights on 46 planes that had not undergone mandatory repairs.
In that case, Southwest paid a fine of $7.5 million, negotiated down from an original FAA proposal of $10.2 million.
