FAA investigators also determined that ATS failed to follow required procedures for placing the airplanes on jacks and stabilizing them. All of the work was done under the supervision of Southwest Airlines, which was responsible for ensuring that procedures were properly followed. 

Southwest returned the jetliners to service and operated them when they were not in compliance with Federal Aviation Regulations, the FAA alleges. The regulatory violations charged involve numerous flights that occurred in 2009 after the FAA put the airline on notice that these aircraft were not in compliance with either FAA Airworthiness Directives or alternate, FAA-approved methods of complying with the directives. The FAA later approved the repairs after the airline provided proper documentation that the repairs met safety standards “Safety is our top priority, and that means holding airlines responsible for the repairs their contractors undertake,” said U.S. Transportation Secretary Anthony Foxx. “Everyone has a role to play and a responsibility to ensure the safety of our transportation system.” 

During its investigation, the FAA found that ATS workers applied sealant beneath the new skin panels but did not install fasteners in all of the rivet holes during the timeframe for the sealant to be effective. This could have resulted in gaps between the skin and the surface to which it was being mounted. Such gaps could allow moisture to penetrate the skin and lead to corrosion. As a result of the improper repairs, these airplanes did not comply with Federal Aviation Regulations.