The relentless snow and ice storms in the United States this winter have led to the most flight cancellations in more than 25 years, according to an analysis by The Associated Press.

U.S. airlines have cancelled more than 75,000 domestic flights since Dec. 1, including roughly 14,000 this week. That's 5.5 per cent of the 1.35 million flights scheduled during that period, according to AP calculations based on information provided by flight tracking site FlightAware.

It's the highest total number and highest per cent of cancellations since at least the winter of 1987-1988, when the Department of Transportation first started collecting cancellation data.

Mother Nature isn't entirely to blame. A mix of cost-cutting measures and new government regulations has made airlines more likely to cancel flights and leave travellers scrambling to get to their destination.

Airlines cutting unprofitable flights

On Thursday, more than 70 per cent of flights were cancelled in Baltimore, Philadelphia, Washington, D.C., and Charlotte, N.C., thanks to a winter storm that paralyzed most air traffic along the East Coast. Ice storms this winter have also caused major headaches in typically warm cities like Atlanta, Dallas and Houston.

"This year is off to a brutal start for airlines and travellers," says FlightAware CEO Daniel Baker. "Not only is each storm causing tens of thousands of cancellations, but there's been a lot of them."

Making things worse, airlines have been cutting unprofitable flights and packing more passengers into planes. That's been great for their bottom line but has created a nightmare for passengers whose flights are cancelled because of a storm. Other planes are too full to easily accommodate the stranded travellers. Many must wait days to secure a seat on another flight.

This winter is even more painful than 2000-2001, when 66,000 — or 4.2 per cent of December, January and February scheduled flights — were scrapped.

"As an industry, you are prepared for bad weather, but I'm not sure if you are ready for this many events back to back," says Savanthi Syth, an airline analyst with Raymond James.

Cancellations being done earlier

Airlines are quicker to cancel flights these days, sometimes a day in advance of a storm. The shift in strategy came in response to new government regulations, improvements to overall operations and because cancelling quickly reduces expenses.

In May 2010, a new DOT rule took effect prohibiting airlines from keeping passengers on the tarmac for three hours or more. So, airlines now choose to cancel blocks of flights to avoid potential fines of up to $27,500 per passenger.

Additionally, the government implemented a new rule at the start of January, increasing the amount of rest pilots need. That's made it harder to operate an irregular schedule, such as those seen after a storm.

Airlines have also learned in recent years that while a large number of early cancellations might cause short-term pain, it helps them better reset after the weather clears. Keeping planes at airports outside of the storm's path can protect equipment and thereby get flight schedules back to normal quickly after a storm passes and airports reopen.

There are also financial considerations. A plane circling above an airport hoping to land, or even one waiting on a taxiway, burns a lot of fuel.

Flying during a winter storm also requires deicing, a process that takes time and costs the airlines money.