Investigators probe Southwest's compliance

DALLAS, July 16 (UPI) -- An investigation into why a hole appeared in a Southwest Airlines jet may turn on whether the carrier met a regulation it previously violated, officials said.

The National Transportation Safety Board, which is investigating the emergency landing of a Southwest jetliner at a Charleston, W.Va., airport, said a 2004 regulation applied to the Boeing 737 that developed a football-sized hole in the fuselage, the Dallas Morning News reported Thursday.

However, the Federal Aviation Administration said the regulation didn't cover the particular part of the plane that failed, and Boeing and Southwest both satisfied regulators with a design improvement, the newspaper said.

In 2008, Southwest was fined after it was determined the carrier violated federal regulations by continuing to fly 46 jets that needed to be inspected for structural damage. The regulation directs owners of some Boeing models to regularly inspect the top of the plane, where sections of the metal "skin" may be altered to reduce weight, possibly making the metal more susceptible to failure, the Dallas newspaper said.

"It looks like that (regulation) would apply," NTSB spokesman Peter Knudson said Wednesday. "We are going to look at the maintenance records and the maintenance practices, and we are going to want to know if all of these (regulations) were followed."