DALLAS (AP) _ A judge's back-to-work prescription for American Airlines' pilots hasn't cured the labor clash that has grounded hundreds of flights and stranded thousands of passengers across the country for nearly a week.

Pilots calling in sick and refusing to fly overtime grounded more than half of American Airlines' 2,250 scheduled flights Thursday, a day after a federal judge ordered them to return to the air.

The 1,170 cancellations _ the most in a single day since problems began Saturday _ left angry passengers stuck in airports as the Presidents Day holiday weekend drew near.

Lucia Bernan fretted about how she and her 4-year-old daughter, Melanie, would get home to Caracas, Venezuela, after their flight out of Miami was canceled.

``Everything is so disorganized that it's extremely hard to believe this is actually happening,'' she said.

U.S. District Judge Joe Kendall, who on Wednesday ordered pilots back to work, scheduled a hearing in Dallas today on the airline's request to hold the Allied Pilots Association in contempt.

Even if pilots return to work immediately, travel is expected to be disrupted for days as planes and crews are moved from city to city.

Overall, more than 3,800 flights have been canceled since Saturday, affecting more than 380,000 travelers. Analysts have predicted the airline will lose millions of dollars.

American estimated that 2,400 of its 9,400 pilots _ one in every four _ called in sick Thursday.

``We're surprised by the conduct of the union leadership,'' said John Hotard, a spokesman for AMR Corp., the Fort Worth, Texas-based parent company of American.

Union President Rich LaVoy urged pilots to return to work. But during a previous pilot sickout against American in 1990, many failed to return despite a court order.

Pilots are disgruntled over pay disparities that have resulted from American's slow integration of recently purchased Reno Air. Some Reno pilots' pay is half the $164,000 a year that an experienced American pilot is paid.

AMR said the pilot union's demands to add Reno pilots to the higher pay scale more quickly would cost as much as $50 million this year, and no progress has been reported in negotiations.

American pilots are barred by federal law from striking over the issue, but federal regulations require pilots to call in sick if they think they are undue emotional stress.

Capt. Jim Philpot, a union spokesman, said: ``We are meeting or exceeding the judge's requirements.''

For now, passengers were still trying to reschedule or get refunds, swamping American's reservation desk with calls and finding themselves disconnected or waiting on hold.

George and Midge Griffin of Cincinnati had been at Chicago's O'Hare International Airport since Wednesday trying to get a flight to Ecuador to visit their daughter. They'd purchased discount tickets, which gave their travel plans a low priority.

``We're at the bottom of the barrel,'' Griffin said.

The couple had been bumped three times in efforts to get on a flight to Miami, which, like Chicago, is one of American's hub operations. The Griffins were trying unsuccessfully Thursday to get a flight back home, with plans to try the trip again in September.