WASHINGTON – The Washington lawmaker who leads the Senate Committee on Commerce, Science and Transportation promised to investigate Southwest Airlines after the carrier canceled thousands of flights on Tuesday, struggling to bounce back from a winter storm while pandemic-related staffing shortages persist.

Sen. Maria Cantwell, a Democrat who chairs the panel, issued a statement while holiday travelers remained stranded at airports across the country despite relatively clear skies after a deadly storm known as a bomb cyclone tore across the United States in the days around Christmas. The storm killed dozens and caused a nationwide transportation meltdown.

“The problems at Southwest Airlines over the last several days go beyond weather,” Cantwell said in a statement. “The Committee will be looking into the causes of these disruptions and its impact to consumers. Many airlines fail to adequately communicate with consumers during flight cancellations. Consumers deserve strong protections, including an updated consumer refund rule.”

As of Tuesday afternoon, Southwest had canceled more than 2,900 flights, which represented nearly two-thirds of the airline’s scheduled trips, according to the flight tracking service FlightAware. The cancellations included most of the airline’s departing and arriving flights in Spokane. By comparison, Spirit had the second most cancellations among U.S. airlines with 93.

The chaos left holiday travelers stranded at airports across the country and was expected to take days to resolve. Southwest canceled 2,909 flights on Monday and, as of Tuesday afternoon, had already canceled 2,476 flights for Wednesday and 1,576 for Thursday, according to FlightAware.

Cantwell, along with two fellow Democrats on the committee, Sens. Richard Blumenthal of Connecticut and Ed Markey of Massachusetts, filed a comment in November urging the U.S. Department of Transportation to strengthen a proposed rule intended to require airlines to compensate travelers for delayed and canceled trips. The senators asked the agency to mandate that a carrier cover room, board and transportation costs when it cancels or “significantly delays” a flight due to a problem within its control.

In a statement posted on Twitter late Monday, the Department of Transportation said it was “concerned by Southwest’s unacceptable rate of cancellations and delays,” and reports of poor customer service, adding that it would “examine whether cancellations were controllable and if Southwest is complying with its customer service plan.”

In a statement issued Tuesday, Southwest offered its “heartfelt apologies” for disruptions it called “unacceptable” and blamed the delays partly on the computer system the company uses to reschedule flights.

“We were fully staffed and prepared for the approaching holiday weekend when the severe weather swept across the continent, where Southwest is the largest carrier in 23 of the top 25 travel markets in the U.S.,” the airline said. “These operational conditions forced daily changes of an unprecedented volume and magnitude to our flight schedule and the tools our teams use to recover the airline remain at capacity.”

Leaders of the House Transportation and Infrastructure Committee, where Rep. Rick Larsen of Everett will be the top Democrat and Rep. Sam Graves, R-Mo., will serve as chairman, did not immediately say whether their panel would also investigate the cancellations.

Congress will reconvene for its 118th session on Jan. 3. Cantwell has not announced a hearing date or the witnesses her committee will call.