A historic winter storm has tangled holiday travel and brought dangerous conditions to a big chunk of the United States, but no airline has struggled more to navigate the Christmas holiday rush than Southwest Airlines.

Southwest canceled more than 2,900 flights Monday — at least 70% of its schedule for the day — and more than 2,500 flights Tuesday as of 9:10 a.m. ET — at least 60% of its schedule, according to flight tracker FlightAware. The disruptions add to chaos that has left people stranded at airports across the country, many of them with little idea of when they can get home or where their bags are.

The number of canceled flights for Southwest Monday was more than 10 times higher than for Delta, which had the second-most cancellations by a U.S. airline with 265 flights called off. Other airlines have also ordered large-scale cancellations in the past week.

Southwest says its crew scheduling process is partly to blame

On Tuesday night, Southwest Airlines CEO Bob Jordan issued a video, pleading with frustrated travelers and frustrated Southwest employees, for patience. Southwest spokesperson Chris Perry told NPR the airline's disruptions are a result of the winter storm's lingering effects, adding that it hopes to "stabilize and improve its operation" with more favorable weather conditions.

Other issues that have exacerbated the airline's struggle to accommodate the holiday rush include problems with "connecting flight crews to their schedules," Perry said. That issue has made it difficult for employees to access crew scheduling services and get reassignments.

Kyle Potter, executive editor of Thrifty Traveler, called it an incredibly complex task for an airline with a network as vast as Southwest's to coordinate staffing and scheduling, particularly after weather delays.

But with many areas seeing clear skies on Monday, the airline would seem to have few obvious reasons to cancel so many flights. Potter calls it a "full-blown meltdown."

"This is really as bad as it gets for an airline," Potter said. "We've seen this again and again over the course of the last year or so, when airlines really just struggle especially after a storm, but there's pretty clear skies across the country."

The airline said in a statement Monday that it will fly about one-third of its schedule for the next several days as it continues to recover its operations.

The U.S. Department of Transportation called the cancellations, delays and customer service response "unacceptable."

"The Department will examine whether cancellations were controllable and if Southwest is complying with its customer service plan," USDOT said in a statement.

Holiday travelers see their plans upended

For Southwest, the situation started unraveling before the Christmas weekend. To have extensive cancellations continue on Monday, Potter said, "is a clear, clear sign something has gone horribly wrong."

From Houston, Texas, and Tampa, Fla., to Cleveland, Ohio, and Denver, Colo., passengers are sharing photos and video of overwhelmed baggage claim areas and long lines at reservation counters. At Southwest, the customer service phone line's hold times averaged more than two hours, sometimes reaching four hours, according to Colorado Public Radio.

"I'm okay with these travel situations and fly on by myself when it's just me, but when my one-year-old has to suffer through it because of ineptitude and mismanagement, that becomes personal," Southwest passenger Joshua Caudle, who said he was unsure when they would be able to leave Denver, said on Denver7 News. "I'm never going to do this with that company again."

A Southwest passenger who says she was attempting to fly from Missouri to Denver said she missed spending Christmas with her family after several delays and cancellations to flights out of the Kansas City International Airport. Despite her being grounded, her luggage was sent to Denver without her, she wrote on Twitter.

Airlines have been hit with renewed demand

Airlines have been struggling to bounce back after losing tens of billions of dollars during the pandemic's worst months. Staffing shortages have plagued airlines as they try to accommodate Americans' return to air travel. And Southwest has not been the only airline to falter under the demand.

Thousands of Delta pilots picketed at major airports this summer, calling for higher pay and highlighting staff concerns as passengers faced flight cancellations during the Fourth of July holiday rush. Last month, Delta pilots voted to authorize a strike after negotiations for a new contract were paused.

"Every airline across the country, Southwest included, got really small at the start of the pandemic when travel basically fell off a cliff, and they have struggled as travel has rebounded to grow back up to 100% and they're still not there," Potter said.