Buttigieg said the airline has pledged to exceed the required level of customer service.

“In order to restore that relationship with their customers, Southwest is going to have to not only make them financially whole, but find a way to really rebuild trust and confidence,” Buttigieg said. “They pledged to me that they’re going to do that. I want to see exactly what that means.”

Last month, the Department of Transportation fined six airlines — including a $2.2 million penalty to Frontier — over what it described as “extreme delays” in customer refund payments.

Potential repercussions could also arise from Capitol Hill. Sens. Ed Markey (D-Mass.) and Richard Blumenthal (D-Conn.) of the Senate Commerce Committee argued that affected fliers are due “significant monetary compensation for the disruption of their holiday plans” that should go beyond ticket refunds and vouchers.

“Southwest is planning to issue a $428 million dividend next year – the company can afford to do right by the consumers it has harmed. Southwest should focus first on its customers stranded at airports and stuck on interminable hold,” the senators said.

A watchdog group blamed Southwest’s failure to invest in updated technology for its slow effort to respond to flight disruptions caused by harsh weather conditions around much of the country.

The group, Accountable.US., called Southwest’s “cancellation crisis a problem of its own making” after it chose “to spend $5.6 billion on stock buybacks in the 3 years leading up to the pandemic rather than making investments in infrastructure to be better prepared for extreme weather events like this week.”

The group said Southwest “even reinstated dividends earlier this month, the first major airline to do so after the pandemic.”

“Southwest Airlines made a risky gamble that mass layoffs and spending billions of dollars on handouts to investors rather than fixing infrastructure would pay off with record profits,” Accountable.US president Kyle Herrig said in a statement. “The airline lost that bet badly and now it’s their customers left paying the price including the thousands stranded in the middle of holiday-season travel.”

Shares of Southwest Airlines were down more than 2% in trading Wednesday. The company’s stock has plunged about 25% since January.

Southwest CEO Bob Jordan issued a public apology for the mess late Tuesday.

“We’re optimistic to be back on track before next week,” Jordan said.

However, the spate of cancellations may have been averted if Jordan heeded a warning from a Southwest executive days before the holiday weekend travel kicked off.

Chris Johnson, Southwest’s vice president of ground operations, circulated a memo to ramp workers on Dec. 21 declaring a “state of operational emergency” at its base in Denver after “an unusually high number” of employees didn’t show up for work, according to Bloomberg News.