What Caused the Chaos at Southwest

Five days after severe winter weather wreaked havoc on holiday air travel across the United States, most major carriers are back up and running. Delta Air Lines, American Airlines and United Airlines each canceled fewer than 40 flights on Wednesday, according to FlightAware, a flight tracking service. Delta had the fewest with only 15 cancellations.

At Southwest, it was a very different story.

More than 2,500 flights, or 62 percent of its planned flights on Wednesday, had been canceled, according to FlightAware. And Southwest said in a statement on Wednesday that it planned to fly one third of its scheduled flights for the next several days as it tries to return to normal operations, meaning it would continue to cancel close to 2,500 flights a day. Some passengers, unable to rebook Southwest flights, rented cars or spent hundreds of dollars to buy tickets on other airlines.

So what caused the meltdown?

The “point-to-point” model failed

Southwest uses a “point-to-point” route model that often lets passengers fly directly from smaller cities and regions without having to stop at a central hub like Denver or New York. Point-to-point flights cut travel times by eliminating the intermediate stop — typically a big advantage for travelers who are not flying from major metro areas.

Other large carriers like United and American rely on a “hub-and-spoke” model in which planes typically fly from smaller cities to a hub airport where passengers change planes.

For example, a passenger flying on a United plane from Oklahoma City to Phoenix may have to stop in Denver for several hours. Southwest flies routes directly from Oklahoma City to Phoenix in less than three hours.

With a hub system, there’s a ready pool of crew members and pilots who can report to work at a major airport, said Mike Arnot, an industry analyst. That makes it easier to regroup after a storm, he said. Planes also are kept closer to their home airports, rather than being spread across the country.

It’s harder to have a reserve of standby crew members and pilots when airlines serve many smaller markets. There is not usually excess crew in places like Syracuse, N.Y., Mr. Arnot said.

As a result, Southwest’s cancellations created a giant snowball effect that rippled across its carefully choreographed network, leaving planes and crews scattered across the country, he and other analysts said.

“The only way to reset is to get the planes and crew back to where they should be,” Mr. Arnot said. “And the only way to do that is to cancel a huge amount of flights.”

In a video message on Tuesday, Southwest’s chief executive, Bob Jordan, likened the airline’s route model to a “giant puzzle” that relies on airplanes and crews remaining in motion.

Because Southwest is the largest airline in 23 of the top 25 travel markets in the United States, when the severe weather led to many canceled flights, it resulted in airplanes and crew members being out of position in dozens of cities, he said.

The airline, he said, was “focused on safely getting all the pieces back into position to end this rolling struggle.”

Tech problems also hurt

Airline scheduling is a “very intricate system” that must take into account union rules, federal regulations and airline policies when assigning crews and pilots to flights, said Kathleen Bangs, a former commercial airline pilot and spokeswoman for FlightAware.

Southwest’s system, however, couldn’t keep track of where its crew members and pilots were after so many flights were canceled, Mr. Arnot said.

Pilots and crew members looking for their next assignment waited hours — nine hours in one case — to speak to staff members at Southwest’s overwhelmed operations center, said Casey A. Murray, president of the Southwest Airlines Pilots Association, the union that represents the almost 10,000 Southwest pilots. With nowhere to go, hundreds of pilots and crew members slept in airports next to passengers and luggage, he said.

“Once one card falls, the whole house falls here at Southwest,” he said. “That’s our problem. We couldn’t keep up with the cascading events.”

Mr. Murray said the union had been urging the airline for years to update “I.T. and infrastructure from the 1990s.”

“We’re seeing these meltdowns occur with more severity and more frequency and this past weekend was the exclamation point,” he said. The airline also suffered a technology meltdown in June 2021 that resulted in a day when half of its flights were delayed and many were canceled; it took days before the situation could be resolved. In October of that year, it had similar issues and canceled more than 1,800 flights over one weekend.

Even before this week’s problems, Mr. Jordan, Southwest’s chief executive, had acknowledged that the scheduling system was outdated.

“We’re behind,” Mr. Jordan said in November, according to Fortune. “As we’ve grown, we’ve outrun our tools.”

For example, Southwest does not have a quick, automated way to contact crew members who get reassigned, he said. “Someone needs to call them or chase them down in the airport and tell them,” he said.

Customers were left with few options

Unlike other major carriers, Southwest does not have agreements with other airlines that allow passengers to fly on competitors’ planes when there is a cancellation or significant delay. “Most low-cost carriers do not have these agreements in place,” Mr. Arnot said, largely because those agreements are expensive.

“If your flight is canceled, you are compensated,” he said of Southwest passengers. Or passengers are rebooked on the next available flight with the same airline.

For thousands of Southwest passengers in the last few days that was not a viable alternative.

Katie McNamara, an art director from Brooklyn, visited family in Mississippi for the holiday with her husband, Justin, and their two children, who are 8 and 2.

They were scheduled to fly back on Wednesday from New Orleans but when their flight was canceled, they could find no other flights on Southwest’s website until at least Jan. 31.

They paid $1,500 for four one-way tickets to New York on JetBlue on Friday. Ms. McNamara said she hoped Southwest will cover the extra cost but was waiting to call customer service. (The airline directed customers to a website to rebook flights or request refunds.)

“I doubt they’re answering their phones at the moment,” she said.

Southwest said that “requests for reasonable reimbursements directly related to the travel disruption” would be reviewed on a case-by-case basis.

Ms. McNamara, 37, who has used Southwest for years for direct flights to visit family in Texas, New Mexico and Mississippi, said the current fiasco won’t keep her from booking with the airline again.