The Federal Aviation Administration announced Monday that it intends to fine Southwest Airlines $12 million for flying Boeing 737 airplanes without making proper repairs.

Beginning in 2006, Southwest began "extreme makeover" alterations to address cracking of aluminum skin on 44 jetliners, the FAA said in a news release.

The agency's investigation found that Aviation Technical Services Inc., a Southwest contractor, failed to follow proper procedures during repairs. "All of the work was done under the supervision of Southwest Airlines, which was responsible for ensuring that procedures were properly followed," the FAA contends.

Southwest then returned the jetliners to service even though they were not in compliance with federal regulations.

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