FORT WORTH, Texas — American Airlines canceled about 300 flights Wednesday so its crews could inspect some wire bundles aboard its MD-80 aircraft.

The canceled flights represent about 13 percent of the estimated 2,300 flights that the nation's biggest airline had scheduled for the day. The highest concentrations of the cancellations were in the airline's hubs at Dallas-Fort Worth and Chicago O'Hare international airports.

American initially put the number of cancellations at 200, but spokesman Tim Wagner said that was a conservative estimate because the airline prefers to hold off on cancellations as long as possible. The entire fleet of MD-80s is being inspected, Wagner said.

The need for the new inspections became known during an audit of American by a joint team of inspectors from the Federal Aviation Administration and the Fort Worth-based airline, Wagner said.

The inspection involves proper spacing between two bundles of wires in the plane's auxiliary hydraulic system, Wagner said. It must be installed "exactly according to the directive," he said.

Wagner did not have an estimate of how many planes had completed the inspection and returned to service, and he couldn't say whether cancellations would continue into Thursday.

"We are in the process of completing the inspections on the remaining airplanes and will return them to service on a rolling basis throughout the day," Wagner said.

About 80 departures were canceled in Dallas-Fort Worth and another 67 were grounded in Chicago, Wagner said.

Shares of American's parent AMR Corp. fell $1.01, or 10.55 percent, to $8.62 in late trading Wednesday, approaching the lower end of their 52-week range of $8.38 to $34.