Feb. 1--American Airlines Inc. said 143 pilots retired Thursday, an unusually high monthly number that the carrier says was caused by the falling stock market, as pilots decided to lock in the value of retirement plans.

In Dallas-Fort Worth, union officials told pilots that 56 of their locally based colleagues had retired.

Anticipating the retirements, the carrier last month canceled 28 flights that it had intended to operate in February, mostly on long-distance international routes that used American's newest and largest airplanes, the Boeing 777.

"Although this represents an unusual number of retirements, it is about on par with what we anticipated," American spokesman Sue Gordon said Thursday. "We made the decision to cancel a limited number of select flights in February. These cancellations represent a small fraction of our February schedule."

She said American has notified customers on the affected flights and is trying to accommodate them on other flights.

"We will continue to monitor the situation and will make further adjustments, if needed," she said.