WASHINGTON — Sometimes it seems like airline passengers just can’t win: The government cracks down on airlines that keep people cooped up on planes that sit on airport tarmacs for endless hours, and carriers cancel more flights to avoid hefty fines.

The Transportation Department’s $900,000 fine Monday against an American Airlines regional affiliate for holding hundreds of passengers on board 15 planes for hours earlier this year may only fuel more debate over whether the get-tough policy is making air travel better or worse for passengers.

POLICY’S IMPACT DEBATED

Transportation Secretary Ray LaHood has hailed as a success the three-hour limit on such tarmac delays. Between May 2010 and April 2011, the first 12 months after the time limit was in effect, airlines reported 20 tarmac delays of more than three hours, none of which was more than four hours long.

In contrast, during the 12 months before the rule took effect, airlines had 693 tarmac delays of more than three hours, and 105 of the delays were longer than four hours.

But a recent Government Accountability Office report concluded, “The rule appears to be associated with an increased number of cancellations for thousands of additional passengers – far more than DOT initially predicted – including some who might not have experienced a tarmac delay.”

With Monday’s fine against American Eagle Airlines, the first imposed under the new rule, cancellations will shoot up even more, airline analyst Michael Boyd said.

“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, an ex-Federal Aviation Administration chief counsel who now represents airlines, said the three-hour limit is “having an inadvertent and anti-consumer effect.”

HARTFORD INCIDENT WATCHED

Airlines that violate the rule can be fined up to $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 to be paid by an airline in a consumer protection case not involving civil rights violations. Airlines have paid much higher fines for federal safety violations.

The DOT “understands that many of these instances are outside of an airline’s control,” said Steve Lott, spokesman for the Air Transport Association, representing major carriers. There may be a shortage of Customs officials on hand for international flights, or an airport may not have enough buses to transport passengers to the terminal.

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

American Eagle held passengers for more than three hours on 15 flights arriving at O’Hare International Airport in Chicago on May 29, according to a settlement agreement between the DOT and the airline.

NO GATES FOR THE PLANES

Poor weather that day had intermittently kept scheduled flights from leaving O’Hare, including American Eagle flights that were sitting at the airline’s gates. But the carrier kept sending planes from other airports into O’Hare, although airline officials knew there were no gates for the planes.

The airline must pay $650,000 of the fine within 30 days, the DOT said. But up to $250,000 can be credited for refunds, vouchers and frequent flier mile awards provided to the 608 passengers on the 15 flights, as well as to passengers on future flights that violate the three-hour rule, the DOT said.

“We think airline passengers deserve to be treated fairly – before, during, and after their flights,” LaHood said in a blog posted by his office. “The tarmac delay rule and vigilant enforcement by DOT are critical steps toward ensuring they are.”

American Eagle said it has apologized and provided either travel vouchers or frequent flier program mileage credit.