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US airlines have canceled more than 1,200 flights Monday as a powerful winter storm packing rain, sleet and snow slammed the East Coast on the holiday weekend and made travel difficult. On Sunday, roughly 3,000 flights were canceled.

Almost 95% of the flights out of Charlotte Douglas International Airport in North Carolina, an American Airlines hub, are canceled, according to flight tracking site FlightAware. The carrier preemptively canceled 1,100 flights Sunday across its mainline and regional operations after canceling 90 Saturday.

“This weekend’s winter storm is expected to have a significant impact on our operation, especially at Charlotte International Airport,” American said in a statement. It also issued a travel notice allowing customers affected by the weather to rebook flights without a fee.

“This weekend’s winter storm is expected to have a significant impact on our operation, especially at Charlotte International Airport (CLT),” American said in a statement.

The airline also issued a travel notice allowing customers affected by the weather to rebook flights without a fee.

Ronald Reagan Washington National Airport is the second-most affected airport, with 38 cancellations reported Monday.

A massive storm system slammed the eastern United States and the Midwest over the weekend. There were reports of crippling ice in parts of Georgia, Virginia and the Carolinas on Sunday. The governors of those states have declared emergencies.

“This is by far going to be the biggest issue we encounter over the next 48 hours: ice, and a lot of it,” CNN meteorologist Allison Chinchar said Saturday morning.

Monday is Martin Luther King, Jr., Day, a federal holiday, and many schools and offices were closed.

American isn’t the only carrier canceling flights. As of 8 am ET Monday, Southwest (LUV) canceled 72 flights, according to FlightAware, while Delta Air Lines (DAL) canceled 37 flights. JetBlue (JBLU) canceled 49 flights and 82 flights on United have been axed.

Other airports in the Southeast also face significant cancellations on Sunday. Raleigh-Durham International Airport in North Carolina has canceled 90 flights, 60%of its trips for the day. Atlanta’s Hartsfield-Jackson International Airport has canceled 27%, or 220, of its flights Sunday. Reagan National near Washington, D.C. has canceled a third of its Sunday flights.

Saturday saw more than 450 cancellations and 2,000 delays in the United States as the storm moved to the South.

It’s been a miserable few weeks to be an airline traveler. Winter weather and Omicron surges left 20,000 US flights canceled over the busy holiday travel season. As travel picked up, staffing cuts also left airlines with fewer employees than they had before the pandemic.

CNN’s Jason Hanna, Hannah Gard, Alanne Orjoux and Chris Isidore contributed to this report.