While a recent blizzard struck much of the United States and affected many airlines and travelers this holiday season, Southwest Airlines continues to suffer, canceling more than 5,500 flights within 48 hours. For comparison, the second-most cancellations over the last two days fell to Delta Air Lines, which only had 311 cancellations. Southwest’s total meltdown marks one of the worst among all airlines in decades, leaving the travel industry wondering how something like this could happen.

In fact, as of the morning of Dec. 28, out of the 2,770 cancellations already made for flights in and out of the country today, 2,507 are operated by Southwest, according to FlightAware. On Dec. 27, 2,694 of the more than 3,200 canceled flights in and out of the United States were Southwest Airlines flights.

A combination of factors led to the breakdown of service, including staff shortages from COVID-19, outdated computer systems used by Southwest Airlines crew, and a bout of the flu and RSV sweeping through Southwest Airlines’ employees. While sickness remains an issue that cannot be easily controlled, outdated systems leading to a breakdown of this magnitude are within the airline’s control and will obviously lead future travelers to secondguess booking Southwest.

Now, thousands of passengers try to get home. Some never even reached their destinations for Christmas, carrying unopened gifts with them in airports. Passengers have also been spotted sleeping on airport floors as they wait for flights. Recent viral videos on social media depict passengers of canceled Southwest flights piling into a rental car, all strangers to one another, and driving hours to their intended destination. Denver International Airport sees the most cancellations today, Dec. 28, with Dallas Love Field and Chicago Midway following close behind.

The meltdown reached U.S. Secretary of Transportation Pete Buttigieg, who plans to hold the airline accountable for their errors and responsibilities. Buttigieg continues to speak with Southwest Airlines CEO Bob Jordan to fix the problems and get passengers to their destinations as soon as possible.

Passengers of canceled Southwest flights are encouraged to keep all receipts of payment, from hotel receipts to rental car receipts. Many passengers already rebooked flights on different airlines, as Southwest Airlines continues to struggle to manage the influx of complaints and re-bookings, as well as the potential for more canceled flights in the coming days.