Southwest Airlines Co led U.S. airline cancellations on Tuesday as the low-cost carrier struggled to recover from harsh winter weather that has wrecked holiday plans for many.

Shares of the Dallas-based airline were down 3.4% at $34.90 before the bell, after it canceled 2,503 flights as of Tuesday 5.50 am ET and another 2,474 for Wednesday, according to tracking website FlightAware.

An arctic blast and a massive winter storm dubbed Elliott swept over much of the United States in the lead-up to the Christmas holiday weekend, forcing Southwest to scrap more than 12,000 flights since Friday. Other airlines have also called off flights, though on a much smaller scale.

Southwest earns most of its profits from flying domestically and unlike other large U.S. carriers, it relies more on point-to-point service instead of operating out of large hubs. That leaves its staff vulnerable to being stranded in case of disruptions.

"We expect Southwest to call out the impact (from the storm) as it was worse than the industry and likely hurt earnings more than a 'normal' storm," Cowen analyst Helane Becker said in a note.

"The other airlines likely had manageable cancellations and delays, and actually appear to have recovered (in time to get everyone home)."

Southwest said on Monday it had decided to continue operating a reduced schedule by flying roughly one third of its schedule "for the next several days."

Its troubles have invited scrutiny from the U.S. Transportation Department, which late on Monday said it would examine the large number of canceled and delayed flights in recent days to determine if they were in the airline's control, branding them "unacceptable."

In total, U.S. airlines have canceled more than 5,000 flights for Tuesday and Wednesday, as of Tuesday morning.

(Reporting by Kannaki Deka and Abhijith Ganapavaram in Bengaluru; Editing by Devika Syamnath)