DALLAS_American Airlines and Delta Air Lines canceled hundreds more flights Thursday as they continued inspections of wiring bundles on some of their planes.

Although thousands of passengers were inconvenienced over the past two days, analysts downplayed any notion that the cancellations would hurt the airlines financially. They said the costs would pale in comparison to high fuel prices.

Delta expected to cancel about 275 flights, or about 3 percent of its schedule, before returning to normal operations early Friday, said spokeswoman Chris Kelly.

American, the nation's largest airline, canceled 141 flights by mid-afternoon Thursday, or about 6 percent of its estimated 2,300 flights, officials said. The Fort Worth-based airline canceled 318 flights Wednesday.

At American, inspectors from the airline and the Federal Aviation Administration focused on fixing the spacing between cords used to secure bundles of wires in the auxiliary hydraulic systems of its MD-80 aircraft.

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

American completed inspections and in some cases alterations on 269 MD-80s by mid-afternoon, and another 21 were still undergoing work that was expected to be done Thursday, Smith said. Nine planes remained to be inspected Thursday night, he said.

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

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.

The inspections came almost three weeks after the FAA ordered a check of maintenance records at all U.S. airlines following criticism of the agency's handling of missed fuselage inspections at Dallas-based Southwest Airlines Co.

The FAA imposed a $10.2 million (€6.5 million) civil penalty on Southwest this month for missing the inspections and then continuing to fly the planes with passengers on board even after realizing the mistake. Southwest officials have said they repaired small cracks in the fuselages of six planes last year and four this month.

The FAA said it would check compliance with at least 10 safety orders at every U.S. airline by Friday. A more complete audit is due by the end of June.

The airlines declined to detail how much they were losing on canceled flights and extra inspections and maintenance.

Shares of American parent AMR Corp. fell 23 cents, or almost 3 percent, to $8.38; and shares of Delta Air Lines Inc. lost 39 cents, or 4.5 percent, to $8.35. For AMR, the closing price was a 52-week low, and Delta shares hit a 52-week low of $8.34 during the session.

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Associated Press Writers Adam Schreck in New York and Daniel Yee in Atlanta contributed to this report.