A powerful winter storm that pummeled much of the United States with freezing rain and heavy snowfall forced airlines to cancel and delay thousands of flights on Monday.

Nearly 19% of scheduled flights were cancelled by late afternoon, according to data from aviation analytics firm Cirium.

Separate data from FlightAware found about 5,220 U.S flights were cancelled and more than 6,500 delayed by early evening. That followed 11,000 flights scrapped on Sunday - the highest daily total since the pandemic, according to Cirium.

A monster winter storm that dumped a foot of snow from New Mexico to New England paralysed much of the eastern US, causing at least 18 deaths. Extreme cold was expected to persist in some places through the week.

Among carriers, American Airlines accounted for the largest share of flight disruptions on Monday, with nearly 1,180 flights cancelled and about 1,130 delayed, followed by Republic Airways, JetBlue Airways and Delta Air Lines.

The Federal Aviation Administration said in an advisory that snow, freezing rain and low visibility had hit major hubs such as Boston and the New York area.

Boston Logan International Airport had the highest rate of cancelled flights on Monday at 71%, Cirium said.

American said the storm disrupted five of its nine hub airports, including its largest base at Dallas–Fort Worth, where freezing temperatures and ice halted flights.

American Airlines requested ground stops from FAA for all of its flights at Dallas–Fort Worth and Ronald Reagan Washington National Airport to manage gate capacity constraints.

The carrier said teams were working around the clock to restore operations.

Passengers inundated carriers with queries on social media platforms as they sought to get to their destinations.

United Airlines said it would begin restoring flights, and its cancellations had dropped sharply from 1,019 on Sunday to 320 on Monday by the evening, according to FlightAware.

The storm was set to become the costliest severe weather event since the Los Angeles-area wildfires in early 2025, with preliminary damage and economic losses estimated at $105 billion to $115 billion, AccuWeather said.

Airline operations are highly interconnected, meaning cancellations can leave aircraft and crews out of position, complicating efforts to restore normal flight schedules.

About 285 scheduled flights on Tuesday have already been cancelled, according to data from FlightAware.