DALLAS — American Airlines and Delta Air Lines canceled hundreds more flights Thursday as they kept inspecting wiring bundles on some of their planes.

American, the nation's largest airline, said it canceled 132 of its estimated 2,300 flights scheduled for Thursday. That was about 6 percent of American's Thursday schedule after the airline canceled 318 flights on Wednesday, spokesman Tim Smith said.

The carrier found seats for most passengers on other planes but also put some customers on other airlines' flights, Smith said.

Delta said it expects about 275 cancellations through early Friday, affecting about 3 percent of its worldwide schedule. Spokeswoman Chris Kelly said about 70 percent of its MD-88 fleet was to be inspected by early evening Thursday, with normal operations planned by early the next day.

Kelly said she didn't yet have estimates on how many passengers were affected.

The inspections come almost three weeks after the Federal Aviation Administration ordered a check of all U.S. airlines' maintenance records. That followed controversy over its handling of missed safety inspections at Dallas-based Southwest Airlines.

American said it began its inspections after a joint audit by its own inspectors and those from the FAA. The inspections focused on proper spacing between cords used to secure bundles of wires in the planes' auxiliary hydraulic system.

"In no way was safety compromised, but the (FAA) directive said 'Do it this way,"' Smith said.

Fort Worth-based American has inspected 243 MD-80 aircraft, and expected to complete inspections and work on 47 other planes and return them to service Thursday, Smith said. Nine planes were expected to be finished Thursday night, he said.

The largest number of flight cancelations, 42, were departures from Dallas-Fort Worth International Airport, with 22 departures scrubbed at Chicago O'Hare, Smith said. Flights from those airports are more likely to use MD-80s, while some airports, such as Miami, were barely affected, he said.

Delta expected heavy volumes Thursday at its hub at Hartsfield-Jackson Atlanta International Airport, Kelly said. Both Delta and the Transportation Security Administration were bringing in extra staff to handle the crowd of travelers, she said.

Earlier this month, the FAA hit Southwest with a $10.2 million civil penalty for missing the safety inspections and then continuing to fly the planes with passengers on board even after realizing the mistake. Southwest has said it will appeal the penalty.

The FAA said then that it would check compliance at every airline with at least 10 safety orders, called airworthiness directives, by March 28. The agency said a full audit covering at least 10 percent of all safety directives will be finished by June 30.

Southwest said it reported the missed inspections itself, and that manufacturer Boeing agreed that keeping the planes in operation until they could be re-examined within 10 days didn't pose a safety hazard. Six of the jets required repairs for small cracks. Those repairs have been completed and the planes returned to service, Southwest spokeswoman Marilee McKinnis said Thursday.

Shares of American parent AMR Corp. rose 1 cent to $8.62, while shares of Delta Air Lines Inc. lost 22 cents, or 2.5 percent, to $8.52 after hitting a 52-week low of $8.39 earlier in the session.

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Associated Press Writer Daniel Yee in Atlanta contributed to this report.