WASHINGTON (AP) — The Federal Aviation Administration said Monday it is proposing a $12 million civil fine against Southwest Airlines for failing to comply with U.S. safety regulations related to repairs on Boeing 737 jetliners. An FAA investigation determined that Southwest's contractor, Aviation Technical Services Inc. of Everett, Washington, failed to follow proper procedures for replacing the fuselage as well as other work on the planes, the agency said. During its investigation, the FAA also found that Aviation Technical Services' workers applied sealant beneath the new skin panels but did not install fasteners in all of the rivet holes fast enough for the sealant to be effective. The FAA also said that Southwest failed to properly install a ground wire on water drain masts on two of its Boeing 737s in response to a safety order aimed at preventing lightning strikes.