4,100 flights already axed as cancellations stretch into Monday.

It’s been a rough holiday weekend for air travel.

Airlines have canceled more than 4,100 flights in the United States since Friday, with disruptions already extending into Monday.

The culprit has been a potent winter storm – dubbed “Harper” by The Weather Channel – that’s brought heavy snow, rain and strong winds to airports from the Great Plains and Midwest into the Northeast and New England.

On Sunday, more than 1,350 flights had been canceled nationwide and another 564 delayed as of 9:25 a.m. ET, according to flight-tracking service FlightAware.

Many of those cancellations were made pre-emptively by airlines by Saturday, in anticipation of poor weather. Sunday’s cancellations punctated what’s already been a difficult week for flying, adding to the 2,165 cancellations reported on Saturday and 522 on Friday, when the storm first began affecting flights in the Midwest and Great Plains.

By far the hardest-hit airport on Sunday was Boston, where about 450 combined arrivals and cancellations had been canceled by early Sunday morning. The majority of those cancellations also had been made preemptively by Saturday. In total, Sunday’s cancellations accounted for about half of the entire day’s schedule there.

In Boston, it appeared that the storm would end there with heavy rain and thunderstorms. But plunging temperatures and a flash freeze could cause problems in and around the airport, including for those trying to get to or from the terminals by car.

Elsewhere, snowy and icy conditions persisted in parts of New England, but were expected to wind down by the day’s end. In interior parts of Pennsylvania and New York state, some locations reported 1 to 2 feet of snow.

Unfortunately for flyers, Sunday’s cancellations went far beyond Boston.

More than 100 combined arrivals and departures had been canceled at New York JFK and nearly 150 at Chicago O’Hare. That accounted for between 5 and 10 percent of the day’s schedule at those airports.

It was a similar story at other major hubs, including Philadelphia, Washington Reagan National, Newark Liberty and New York LaGuardia, where cancellations had already wiped from 5 to 15 percent of the day’s flights off Sunday’s schedule at those airports. More were problems were possible from residual disruptions in the wake of the storm.
At smaller and mid-sized airports away from the coast, flight schedules took a major hit because of heavy snow or ice.

In New York state, FlightAware calculated roughly half the day’s flights had been canceled at airports in Albany, Syracuse and Rochester. It was a similar story across the state line in Burlington, Vermont, where the 31 combined arrival and departure cancellations accounted for more than half the schedule there. At Connecticut’s Bradley airport near Hartford, 70 flights – also about half the day’s schedule – had been scrapped as of early Sunday, according to FlightAware’s count.

Among the many other smaller airports seeing major cancellation counts on Sunday were Allentown, State College and Wilkes-Barre/Scranton in Pennsylvania; Manchester in New Hampshire; and Bangor and Portland in Maine.

Looking ahead to Monday, more than 110 flights had already been canceled. Of those, FlightAware counted 46 on JetBlue and at least 58 on American and its American Eagle regional affiliates.

The airports with the most pre-emptive cancellations for Monday were Washington Reagan National (40 combined arrival and departure cancellations), Boston (36), Charlotte (14), Philadelphia (11) and New York JFK (10). More cancellations were possible as airlines worked to get their operations back to normal after the storm.