Thousands of Canceled Flights Upend Travel Plans Across U.S.

Southwest Airlines said in a statement on Monday that the travel disruptions were “unacceptable” and that its network was behind because of the winter storm that slammed parts of the country with heavy snow, ice and strong winds much of last week. “Our heartfelt apologies for this are just beginning,” the company said, adding that it was working to address the disruptions by “rebalancing the airline and repositioning” crews.

By late Monday and into Tuesday morning, Southwest was in damage-control mode, responding to angry and frustrated customers on Twitter. The airline repeatedly apologized for the cancellations and offered assistance through direct messages, which did not appease everyone. The U.S. Department of Transportation said in a statement on Monday that it would look into the Southwest issue, adding that it was concerned by the airline’s “unacceptable rate of cancellations and delays” and reports of poor customer service.

Southwest’s network is organized in what is known as a point-to-point system, according to David Vernon, an airline analyst at the financial firm Sanford C. Bernstein. That type of system enables higher use of planes during normal times but can cause cascading negative effects when things go wrong.

No single region or airport bore the brunt of the cancellations. On Tuesday morning, more than 150 flights originating at Denver International Airport, or about 17 percent of its outgoing traffic, were canceled, and more than 115 flights, or about 38 percent, were canceled out of Chicago Midway International. More than 100 flights were also canceled at Harry Reid International in Las Vegas, and similar numbers were reported for Baltimore-Washington International, Dallas Love Field in Texas and Nashville International in Tennessee.

It’s been nearly a week since the winter storm began wreaking havoc for millions of people counting on airlines to get them from point A to B. The number of canceled flight began to rise last Thursday, with airlines canceling more than 2,600. The next day, nearly 6,000 or about a quarter of all flights were canceled across the U.S. On Christmas Eve, nearly 3,500 flights were canceled and slightly fewer, at about 3,200, were cut from the scheduled on Christmas Day.