With American Airlines threatening legal action, the leader of the pilots' union is telling it members not to delay flights - if that's what they're doing.

Acting President Keith Wilson said that the Allied Pilots Association has nothing to do with what American alleges is a work slowdown that is causing many flights to be delayed or canceled.

If, as the company charges, pilots are dawdling by filing frivolous maintenance write-ups and flying circuitous routes, "that activity must cease immediately," Wilson said in a memo to members on Thursday night. He said the union had responded quickly this month when rumors surfaced of pilots calling in sick to protest lack of a labor deal with American.

Wilson's memo comes a day after American threatened to haul the union into court if disruptions continued.

American Airlines senior vice president Denise Lynn said that some pilots were conducting "an unlawful, concerted effort to damage the company."

On Thursday, American canceled 100 flights, or 5.4 percent of its schedule, and only 49.9 percent arrived on time, according to FlightStats.com.

- Associated Press