WASHINGTON - The government's $900,000 fine Monday against an American Airlines affiliate for holding hundreds of passengers on board planes for hours on an airport tarmac may serve as a deterrent to future such incidents. But industry analysts warned that may come with the price of more canceled flights.

Even before the fine against American Eagle Airlines, airlines had cancelled more flights to avoid pushing up against the new three-hour limit on tarmac delays. Now, cancellations will shoot up even more, said airline analyst Michael Boyd.

"If there's a 20 percent chance of this happening, an airline will cancel," Boyd said, because of the potential for massive fines.

Ken Quinn, a former Federal Aviation Administration chief counsel who represents airlines, said the limit is "having an inadvertent, anti-consumer effect."

Airlines that violate the rule can be fined as much as $27,500 per passenger, but transportation officials had held off fining air carriers in any of the several dozen instances where the rule has been broken until this week. Industry officials are watching for any action from DOT on a similar incident at the Hartford, Conn., airport during a freak snowstorm in October.

The fine imposed on American Eagle was the largest penalty to be paid by an airline in a consumer protection case not involving civil rights violations, although airlines have paid much higher fines for violating federal safety regulations.

The new DOT rule requires that after three hours airlines must either return the plane to a gate or provide passengers who wish to disembark with some other means of safely getting off. Sometimes that means pulling up a stairway, allowing passengers off and taking them on buses to the terminal. The rule has since been extended to international flight delays, which are capped at four hours.

The transportation department "understands that many of these instances are outside of an airline's control," said Steve Lott, a spokesman for the Air Transport Association, which represents major carriers. Sometimes, airports have a shortage of Customs officials on hand for international flights, or an airport may not have enough buses to transport passengers safely to the terminal, or experience other emergency shortages.

But officials apparently felt the case involving American Eagle was particularly egregious and wanted to send a warning to other carriers the week before Thanksgiving travel.