The nation's recent onslaught of flight cancellations is a harbinger of what passengers can expect from airlines looking to avoid new multimillion-dollar fines for leaving people stranded on grounded planes in bad weather, according to federal data and aviation experts.

The government announced in December it would fine airlines $27,500 per passenger for long tarmac delays — or $2.75 million for a 100-passenger flight.

Cancellations cost far less than a huge fine, especially since seats are routinely prepaid and airlines save fuel cost.

"You're not going to get penalized for tarmac delays if you don't fly the flight," said Massachusetts Institute of Technology professor John Hansman, an aviation expert.

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From Feb. 5 through Thursday, when severe snowstorms hit the Mid-Atlantic and Midwest, airlines canceled about 15,000 flights, according to the Air Transport Association. It took days for the 500,000 to 1 million passengers to rebook.

The fines for lengthy tarmac delays — defined as three hours or more — go into effect April 29. Airlines such as JetBlue Airways have already made the decision that it is better to aggressively drop flights from their schedules when bad weather strikes.

JetBlue changed its own policy about stranded planes after nine of its jets were stuck on the tarmac for at least six hours in a snow and ice storm at New York's John F. Kennedy International Airport on Valentine's Day in 2007.

In 2005 and 2006, the carrier canceled an average of 254 flights a year, according to federal Bureau of Transportation Statistics data. After the Valentine's Day strandings, when the airline set a rule that no flight could be delayed on the ground more than four hours, the figure jumped to 1,223 a year.

JetBlue canceled 387 flights during Wednesday's snowstorms. JetBlue Chief Operating Officer Rob Maruster said those cancellations were done in part so the airline could live up to its own policy about tarmac strandings.

Amy Cohn, an associate professor at the University of Michigan who has done extensive research on airline scheduling, said she had seen a substantial increase in cancellations across the airline industry. "They're canceling a lot more," she said.

Passenger advocates say that airlines don't need to cancel flights to prevent tarmac delays. "This is solvable" without excess cancellations, said Kate Hanni, who founded Flyersrights.org after a flight she was on in 2006 was stranded.

The Department of Transportation authored the three-hour tarmac rule to protect passengers' "fundamental right to be treated with respect," said spokeswoman Maureen Knightly.