Department of Transportation says it's 'concerned by Southwest’s unacceptable rate of cancellations'

The U.S. Department of Transportation said it would look into whether Southwest Airlines' high rate of flight cancellations and delays "were controllable" and in compliance with the company's service plan following the freezing winter storm that swept the nation over the holiday weekend.

"USDOT is concerned by Southwest’s unacceptable rate of cancellations and delays & reports of lack of prompt customer service," the department wrote on Twitter late Monday. "The Department will examine whether cancellations were controllable and if Southwest is complying with its customer service plan."

Southwest canceled more than 2,500 flights scheduled for Tuesday and said it would only fly roughly one-third of its schedule for the next several days as a piercing winter storm continues to batter the U.S. The company released a statement on Monday apologizing for the cancellations and delays, noting that it is repositioning its crews and planes to address the wide-scale disruption.

“With consecutive days of extreme winter weather across our network behind us, continuing challenges are impacting our Customers and Employees in a significant way that is unacceptable,” Southwest Airlines said in the statement. “And our heartfelt apologies for this are just beginning.”

Transportation Secretary Pete Buttigieg also stepped in, saying that he will have “more to say” about Southwest’s cancellations on Tuesday.

Though Southwest is not the only airline impacted by the fallout from the storm, most other major airlines have mostly recovered from the bustling holiday weekend filled with travel issues due to the freezing temperatures and weather.

The holiday storm marked a chaotic end to the year for airlines as they grappled with a resurgence in flying demand. Throughout this year, that high demand led to significant delays and cancellations, especially during summer holiday travel weekends.