Southwest Airlines has bought itself a bunch of new toys for Christmas: planes with larger overhead bins, shiny new deicing trucks, and outdoor heaters that can blast 400,000 Btus of hot air to keep ground crews warm and prevent planes from getting stuck to the tarmac in freezing conditions. Its passengers are getting something, too: a promise that the airline will try not to leave them stranded again.

Last year Southwest was the Grinch. After a massive winter storm blanketed much of the country starting on December 21, the airline’s operations went into a deep freeze. By December 29, Southwest had canceled 16,700 flights—or about 2,500 more flights than all nine other major air carriers canceled, combined, that month. That left more than two million passengers out in the cold. The debacle has already cost the company $1.1 billion and could cost it even more. In October, the U.S. Department of Transportation said a fine would be justified for Southwest’s failure to provide passengers with “adequate customer service assistance, prompt flight status notifications, and proper and prompt refunds.”

To avoid a repeat of that nightmarish Christmas season, Southwest and a team of consultants spent months studying what went wrong and determined that no single factor was responsible for the cascade of cancellations. That meant there was no one fix. “We had all of these kind of individual shortcomings,” says Andrew Watterson, Southwest’s chief operating officer. “Taken together, they made this complex system fall over.”

So Southwest made a litany of changes. It reorganized business units, ponied up for new winter gear, added new functionality to its crew-scheduling software, and hired thousands of new workers. Yet some of the airline’s employees aren’t sure that enough has been done, and even company executives aren’t guaranteeing that in the event of another big storm, Southwest will provide smooth flying in the holiday-packed weeks ahead.

Well before the first snowflakes began to fall on December 21, 2022, Southwest knew it had a big problem. The airline’s union leaders had blasted management for failing to upgrade its crew-scheduling software, among other issues. Casey Murray, president of the Southwest Airlines Pilots Association, had warned a month earlier that he believed the airline might be “one thunderstorm” away from a “complete meltdown.”

So in early December of last year, the airline hired Oliver Wyman, a consulting firm based in New York City, to review how Southwest responds to what it internally calls “irregular events.” Such events, usually triggered by weather, had caused major disruptions in recent years, most notably in October 2021, when the airline canceled more than two thousand flights nationwide over the long Columbus Day weekend, in part because of thunderstorms in Florida and a temporary halting of flights by air traffic controllers. Other airlines brushed off those events. Two days after the storms hit, Southwest canceled 28 percent of its entire schedule for that day, while American Airlines canceled just 2 percent.

Following the 2022 holiday storm, the job of the Oliver Wyman consultants became even more important. They determined that two cities were the epicenter of the mess: Chicago and Denver. “Twenty-five percent of our flight crews are based there,” Watterson says. “And for about twenty-four to thirty-six hours, we operated only a fraction, like ten percent or fifteen percent of our flight schedule there.”

The trouble started in Denver, where Southwest had expanded rapidly in 2022, adding more than a dozen gates and over a hundred new employees. The hub, already the airline’s single biggest in terms of daily departures, got even bigger. But Southwest failed to add enough deicing equipment for all that growth. It had 25 deicing trucks serving roughly 300 daily departures, while its biggest competitor in Denver, United Airlines, had nearly twice as many trucks per flight: 61 for 425. By December 22, a day after the winter storm arrived, Southwest had canceled 384 flights from Denver while United had canceled just 47.

The tires of planes in Denver were freezing to the tarmac in the frigid conditions. That’s why Southwest has bought many more of those powerful outdoor heaters. It has added fifteen deicing trucks at that airport as well, plus four parking spots where planes can be safely deiced. “We also added six hundred more people [across multiple shifts] on the ramp to help,” Watterson says. “And we added new fueling trucks and new blending stations for deicing fluid.” System-wide, the airline has stockpiled an additional 400,000 gallons of propylene glycol—the main component in deicing fluid, as well as in the antifreeze used in car radiators.

But all that new gear hasn’t impressed pilots’ association president Murray, who doesn’t believe a lack of trucks and heaters was the only problem in Denver. He points instead to Southwest’s failure to calculate how much time, in the forecast weather conditions, planes would have to take off after being deiced—known in airline lingo as holdover time. Murray says Southwest, lacking these holdover calculations, was left with no choice but to cancel flights, because flights can’t leave the gate without holdover estimates. Meanwhile, he says, United had its calculations in hand: “United was launching airplanes.” Watterson says that Southwest has invested in a new application that automatically calculates holdover time.

Murray also complains that he was given just one hour with the Oliver Wyman consultants back in late January, and that since then, the pilots’ involvement in Southwest’s changes has been minimal. “They don’t ask us what they should do,” he says. “They tell us what they are doing.”

Discord between the pilots’ union and management is another potential hazard this holiday season. Until the end of this month, the two sides are meeting with federal mediators who are trying to aid in the negotiation of a new labor contract. If that goes poorly, Murray warns that the pilots could be on strike by the end of December. “If I was a paying customer,” he says, “I would be kind of concerned.”

Soon after planes were literally stuck on the ground in Denver, air traffic also ground to a crawl in Chicago, Southwest’s third-busiest city. For two days, because of the weather-related problems in those two cities, nearly 25 percent of the airline’s flight crews weren’t able to get in the air. Southwest couldn’t get them to other airports where it needed them, which resulted in a domino effect of flight cancellations that continued for more than a week. Other airlines weren’t nearly as affected by the winter weather. On December 26, for instance, five days after the storm hit, Southwest canceled 70 percent of its flights, while United canceled just 5 percent and American just under 1 percent.

Compounding the issue, the software systems Southwest uses to cancel flights and to assign crews couldn’t keep up with so many changes at once. The airline knew—as it told employees internally during the meltdown and had told the media weeks before—that its tech tools were insufficient to respond to a major disruption.

When a U.S. Senate committee called Southwest onto the carpet in a February hearing focused on the airline’s holiday failings, Murray testified that the crew-scheduling software was so antiquated that not only was it unable to pair crews with planes after cancellations, it also lost track of where crew members were. Murray said the two separate software systems that Southwest used to process cancellations and “recrew” flights were giving contradictory information to each other, creating a bigger mess for the airline.

As scheduling fell further and further behind, Southwest crew members calling in to get their work assignments were left on hold for hours at a time. Some also ended up having to sleep in airports and pay for their own meals because the airline had lost track of their whereabouts, according to Lyn Montgomery, president of Southwest’s flight attendants’ union. “When you have issues with the basics of food and shelter,” she says, “you are going to have huge problems.”

Although Watterson insists that outdated technology was not the primary cause of the holiday crisis, Southwest budgeted $1.3 billion for tech projects this year, about 25 percent more than in 2019, prior to the industry-wide disruption of the COVID-19 pandemic. Some of that new money went to upgrading the crew-scheduling software with tools to help the airline recover from “a mass cancellation event.” The airline also developed methods for crews to communicate with schedulers digitally, rather than on the phone. Watterson says that change required amendments to the airline’s agreements with its unions. “Our contract had required us to talk to them on a recorded line,” he says.

Southwest has hired more than sixty additional crew schedulers and moved its Network Planning team under the same management as its Network Operations Control team—the people who execute the flight schedule every day. This consolidation is aimed at making sure that flight schedules are created with enough leeway for navigating disruptions. But Montgomery doubts the airline has done everything it should to ensure flight attendants won’t again be sleeping in airports if another major storm blows through. As she puts it, “We’re still approaching the holiday season with the thought of, ‘Oh my gosh, we hope we make it through okay.’ ”

Southwest plans to be much more aggressive than it has in the past about canceling flights whenever the next round of exceptionally disruptive weather approaches. This would enable the airline to keep crews in positions from which they can keep flying even when the skies over one or more big cities get shut down.

“We’ve gone through each airport, especially our bigger airports, especially our crew bases, and we identified how much of our schedule we have to operate [during a disruption] to make sure we get enough flight crews out in the system so that our crew network stays together and doesn’t fall over,” Watterson says. “Once we determined that, we then said, ‘Well, what do we need at Denver, at Chicago, and at other places to make sure we can operate that much of our schedule?’ ”

That’s what led Southwest to buy those new deicing trucks and heaters and all the rest. The airline has stress tested its operations in “war games” this year at Love Field, throwing potential problems at its operations personnel and managers from airports in some of its biggest cities to see how they’d respond. It’s led to changes such as new communication procedures for the sharing of weather alerts among various teams within the company. “It’s been eye-opening,” Watterson says of the exercises, which just wrapped up this week. “We’ve corrected a lot of stuff.” 

All that work toward improvement has given him a sense of cautious optimism that this year will be different. But, he adds, “I won’t let myself have too much confidence until we get through 2023.”