The U.S. Department of Transportation said it will look into flight cancellations by Southwest Airlines that have left travelers stranded at airports across the country amid an intense winter storm that has killed dozens of people.Southwest spokesman Jay McVay said at a press conference in Houston that cancellations snowballed as storm systems moved across the country, leaving flight crews and planes out of place“So we’ve been chasing our tails, trying to catch up and get back to normal safely, which is our number one priority as quickly as we could,” he said.“And that’s exactly how we ended up where we are today.”More than 2,800 more flights had already been canceled in the U.S. as of 7 a.m. Tuesday and problems are likely to continue at least into Wednesday.The Department of Transportation said on Twitter that it was “concerned by Southwest’s unacceptable rate of cancellations and delays & reports of lack of prompt customer service.” The tweet said the department would look into whether Southwest could have done anything about the cancellations and whether the airline was complying with its customer service plan.Southwest CEO Bob Jordan told The Wall Street Journal in an interview that the airline would operate just over a third of its usual schedule to allow crews to get back to where they needed to be."