The meltdown at Southwest Airlines continued on Tuesday with another 2,600 cancellations and almost 800 delays as of 4:25 p.m. ET, according to the flight-tracker FlightAware
"Due to adverse weather events and their resulting effects, we are currently experiencing operational disruptions and are working diligently and safely to restore normal flight schedules as quickly as possible," read a statement on the airline's website. 
While the holiday weekend's severe winter weather made trouble for most major airlines, Southwest had it the worst: The company's cancellations made up more than 50 percent of the total for the last few days.  Around 63 percent of the airline's flights were canceled Tuesday. 
That's a slight improvement from Monday, when Southwest canceled more than 70 percent of its flights, but it's still well above the zero to 2 percent cancellation rates from other major airlines such as United, JetBlue, Delta, and American. 
The situation is so dire that federal regulators are already launching an investigation. The U.S. Department of Transportation issued a statement on Monday night calling the rate of cancellations "unacceptable." 
"The Department will examine whether cancellations were controllable and if Southwest is complying with its customer service plan," the agency tweeted. It also shared a link to the airline's customer service policy in an effort to aid stranded travelers looking to rebook. 
Captain Casey Murray, the president of the Southwest Airlines Pilots Association, told CNN that problems have been brewing at the airline for more than a year, and that outdated technology was partly to blame. 
“It’s phones, it’s computers, it’s processing power, it’s the programs used to connect us to airplanes — that’s where the problem lies, and it’s systemic throughout the whole airline,” he said.
Shares of Southwest Airlines were down around 6 percent on Tuesday.