The Associated Press

DALLAS (AP) - Southwest Airlines Co., facing a deadline of Tuesday for settling a dispute with regulators over the use of unapproved parts, said Monday the parts were installed on almost twice as many planes as it first believed.

The airline also has suspended the maintenance firm that got the parts from a subcontractor.

Southwest said Monday it has replaced the unapproved parts in more than 25 planes but needs more time to find parts for the remaining jets and an extension to avoid a disruption in its service to its customers.

Without an extension, the Federal Aviation Administration could force the airline to ground some planes.

FAA officials have said the unapproved parts - designed to push hot engine exhaust away from the wings - didn't pose an immediate safety hazard. On Aug. 22, they gave Southwest 10 days to fix the problem.

Southwest originally said the parts were installed on 46 planes, but spokeswoman Beth Harbin said Monday further checking boosted the number to 82 planes. That sparked a search for more replacement parts.

"Southwest did an exhaustive audit of the vendor, and are comfortable we've found all the parts at issue," she said.

Harbin called the parts "perfectly safe" but acknowledged they were made by a subcontractor who wasn't approved for the work by the FAA. The subcontractor was hired by a maintenance company hired by Southwest.

Harbin said Southwest has suspended the maintenance company, D-Velco. She did not say whether theaction was temporary or permanent. The airline has not identified the subcontractor.

Southwest has more than 500 planes. If the FAA forced Southwest to idle all the planes that still have the unapproved parts, that would be about 10 percent of its fleet of Boeing 737 aircraft. The airline canceled 15 flights and suffered widespread delays when it grounded 46 planes for most of the day on Aug. 22.

Dallas-based Southwest, the nation's biggest discount airline, agreed in March to pay $7.5 million to settle FAA allegations that it operated nearly 60,000 flights using planes that had not been examined for structural cracks as required by federal regulations.

In June, a Southwest jet had to make an emergency landing when a foot-long hole opened in the roof. There were no injuries.

Southwest shares fell 19 cents, or 2.2 percent, to $8.32 in midday trading Monday.