(CNN) — Last week’s winter weather travel mess is lingering like a hangover into this week — and the headaches are particularly bad for Southwest Airlines and its passengers on Monday.

Almost 3,000 flights within, into or out of the US had already been canceled by 2 p.m. ET Monday, according to flight tracking website FlightAware, while more than 4,900 flights had been delayed.

Southwest accounts for a big share of those. The Dallas-headquartered airline has canceled more than half of its flights, or more than 2,000 total flights, on Monday, according to FlightAware.

On social media, customers are complaining about long lines to speak with representatives, problems with lost bags and excessive wait times or busy signals on the airline’s customer service telephone lines.

‘Disruptions across our network’

In a statement to CNN, Southwest Airlines said it is “experiencing disruptions across our network as a result of (the winter storm’s) lingering effects on the totality of our operation.”

Some of the airports seeing the biggest issue are Denver, Las Vegas, Chicago Midway, Baltimore/Washington, and Dallas Love Field where Southwest operates.

Calls to Southwest’s customer service attempted Monday afternoon by CNN did not go through, so customers couldn’t even get in the queue to speak to a representative. Southwest told CNN it is “fully staffed to answer calls.”

The airline also says, “those whose flights have been canceled may request a full refund or receive a flight credit, which does not expire.”

Meanwhile, in hard-hit western New York, Buffalo International Airport said in its most recent tweet that it plans to resume passenger flights at 11 a.m. ET Tuesday.

The temperature at the airport was 18°F (-8°C) around 2 p.m. ET with light snow falling on top of the huge amounts the area has already seen.

Bad road conditions

Road travel remained treacherous in parts of the United States because of extreme wintry conditions.

In New York state’s western Erie County, emergency restrictions on driving were lifted in some communities but remained in place in Buffalo, County Executive Mark Poloncarz said on Monday.

“The City of Buffalo is impassable in most areas, while mains may have a lane open for emergency traffic or two, most secondaries as well as side streets have not been touched yet,” Poloncarz said.

He adding that the cleared main roads are primarily for the use of life-saving measures to open up areas around hospitals and nursing homes.

A rough past week

A winter storm that swept across the United States was ill-timed for travelers who had started pushing Christmas week flying numbers back toward pre-pandemic levels.

On Christmas Day, there were 3,178 flights canceled and 6,870 flight delayed, according to FlightAware.

On Christmas Eve, there were a total of 3,487 flights canceled, according to FlightAware.

Friday was the worst day of this streak with 5,934 cancellations, while Thursday saw almost 2,700 cancellations.

This megablast of winter weather across the eastern two-thirds of the nation is forecast to slowly moderate this week.

More developments to come on this breaking news story.

Almost 3,000 US flights canceled Monday as Southwest Airlines struggles