U.S. Transportation Secretary Pete Buttigieg on Wednesday ratcheted up pressure on Southwest Airlines, saying thousands of more canceled flights indicated a system failure at the low-cost carrier.

"We are past the point where they could say this is a weather-driven issue," Buttigieg said in an interview posted by ABC News on its website. "Don't get me wrong, all of this began with that severe storm. We saw winter weather affecting the country and severely disrupting all airlines."

At least 60 people died nationwide in weather-related incidents in recent days, NBC News reported.

The rest of the aviation system and other airlines seemed to be back from the weather disruptions, Buttigieg said.

"So what this indicates is a system failure (at Southwest), and they need to make sure that these stranded passengers get to where they need to go and that they are provided adequate compensation, not just for the flights itself ... but also things like hotels, like ground transportation, like meals because this is the airlines' responsibility," he said, adding he had spoken to the company's leadership.

U.S. airlines had canceled thousands of flights as a massive winter storm swept over much of the country before and during the Christmas holiday weekend, but Southwest's woes have deepened while other airlines have largely recovered.

Southwest has canceled a total of more than 14,500 flights since Friday. On Wednesday it canceled 2,500 flights, according to the flight tracking website FlightAware.

Southwest told Reuters it would reimburse customers for travel-related costs and had already processed thousands of requests.

It also said employees across the airline were helping crews in many functions.

(Cover: A Southwest Airlines passenger jet lands at Chicago Midway International Airport in Chicago, Illinois, on December 28, 2022. /CFP)