The cliché about a "perfect storm" could hardly be a more apt description of the situation right now for Southwest Airlines — a carrier that has been forced to cancel more than 60% of its flights over the busy Christmas travel season as it struggles to get back on course after a devastating blizzard that socked in much of the United States.

While Southwest isn't the only airline to experience delays and cancellations, it is by far the worst-hit. More than 5,500 Southwest flights have been taken off departure boards across the country in the last two days, compared to 311 cancellations for Delta, which had the second-most cancellations by a U.S. airline.

Analysts say Southwest's problems are the result of a confluence of events — not just the severe weather, but staff shortages caused by the COVID-19 pandemic, as well as employees out sick with influenza and respiratory syncytial virus (RSV). Most important is an outdated computer system for crew scheduling that turned what would have been simply a challenging storm into a full-scale meltdown.

"In short, everything possible has gone wrong for Southwest, including some problems of their own making," says Kyle Potter, executive editor of Thrifty Traveler, a travel website. "At this point, we can very safely say that this is no longer a weather-related disturbance. We've had clear skies in the United States for several days now, more or less, and Southwest is the only airline that is failing so spectacularly here."