The Transportation Department is in the initial phases of an investigation into Southwest Airlines' travel meltdown, and it will look at whether executives overscheduled flights, a spokesperson said.

Southwest canceled thousands of flights, slashing around two-thirds of its daily schedule, for days as it struggled to recover from winter weather even as other airlines managed. Passengers were stranded and scrambled to find other ways to get home.

The Transportation Department is “probing whether Southwest executives engaged in unrealistic scheduling of flights which under federal law is considered an unfair and deceptive practice,” the spokesperson said.

What’s causing Southwest’s mass flight cancellations?

Dec. 29, 202202:39

Southwest said in a statement Wednesday that it was prepared, but there was a massive winter storm. It said it will continue to cooperate with all inquiries.

“Our holiday flight schedule was thoughtfully designed and offered to our Customers with the backing of a solid plan to operate it, and with ample staffing,” Southwest said. “Our systems and processes became stressed while working to recover from multiple days of flight cancelations across 50 airports in the wake of an unprecedented storm.”

The Transportation Department said it was also ensuring Southwest was providing refunds and reimbursements to passengers.

“DOT will leverage the full extent of its investigative and enforcement power to ensure consumers are protected and this process will continue to evolve as the Department learns more,” the department spokesperson said by email Wednesday.

The cancellations, which came after the Christmas holiday, infuriated passengers. Transportation Secretary Pete Buttigieg called them unacceptable and said his department would look at its scheduling system.

Southwest canceled an estimated 11,000 flights in the week after Christmas, and it has pinned the cost of the fiasco at upward of $800 million.