A Southwest Airlines plane takes off as another of the airline’s jets taxis in Burbank, California. Southwest Airlines has announced that it will abandon its 50-year-old open seating policy and instead opt for a seat assignment that includes premium seating to broaden its appeal.

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It’s a big week for Southwest Airlines as the airline prepares to announce more details about its move away from the open seating model that has long been its trademark.

This represents a major change for the Dallas-based airline, one that Southwest has been considering since at least 2006.

“It was a secret project. We had to use code words when we talked about it,” says Doug Lawson, who worked for Southwest for more than 20 years, mostly in operations.

Southwest is known for turning its planes around faster than its competitors, in part because passengers can choose any available seat when boarding. But officials wanted to know if there was an even faster way: boarding from outside to inside, window seats, then middle seats, then aisle seats, sometimes known by the acronym WILMA.

It was so controversial that, according to Lawson, it had to be kept secret – even within Southwest. “The code name was D WILMA,” Lawson said in an interview. “The D stands for ‘Doug.’ My boss couldn’t think of anything more original,” he chuckled.

Finally, in 2006, Southwest lifted the veil of secrecy with a real-life experiment at San Diego International Airport and invited the media (including NPR) to watch.

In some cases, passengers boarded the plane the normal Southwest way, with free seating. In other cases, they were assigned seats according to the WILMA plan. In the end, Lawson recalls, there was a clear winner: WILMA.

“It was about a 20% difference,” Lawson said. “That’s huge. It’s a very significant operational improvement.”

Still, Southwest decided to stick with open seating. Lawson said company executives at the time were concerned that the change could damage the brand.

Back then, Southwest was concerned about keeping its planes in the air because they weren’t making money on the ground. But a lot has changed in the airline industry. Airlines are trying to maximize their profits – even if that slows down the boarding process.

“That’s what our customers want,” Southwest CEO Bob Jordan told CNBC in July. “Eighty percent of customers who fly Southwest said they wanted a designated seat… And when a customer switches from Southwest to another competitor, that’s the number one reason.”

A traveler walks past a Southwest Airlines airplane as it taxis at Baltimore Washington International Thurgood Marshall Airport on October 11, 2021 in Baltimore.

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It’s not just because customers like to choose their seats. Airlines have also discovered that they can make money by selling their seats at a higher price. They’re also putting more emphasis on loyalty programs that reward their best customers with perks like early boarding.

“There is an ideal location here for the airlines that are looking for them,” said Ahmed Abdelghany, a professor at Embry-Riddle Aeronautical University who formerly worked in operations at United Airlines.

“I want to make money,” said Abdelghany. “I want to be efficient. And at the same time, I want to satisfy my customers.”

Over the years, a lot of research has been done on the fastest way to board an airplane. Back in 2005, an astrophysicist named Jason Steffen started working on this problem after he found himself stuck in a long queue. Steffen, who is now a professor at the University of Nevada, Las Vegas, submitted his paper “Optimal Boarding Method for Airline Passengers” to the Journal of Air Traffic Management.

“The fastest way to let people on board is to send them in in such a way that each subsequent passenger has enough space to stow their luggage without colliding with their neighbors,” Steffen said in an interview.

Steffen’s method involves boarding the rows alternately to give passengers more space, while at the same time boarding each row from the outside to the inside.

Passengers line up to check in at the Southwest Airlines ticket counter at Chicago’s Midway Airport. Southwest will soon change its seating policy.

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“You get people on the plane and minimize the number of aisles,” Steffen said. “And the next biggest hindrance is the seats where you have to jump over someone.”

Some airlines have adopted elements of Steffen’s approach. United, for example, has incorporated WILMA principles into its boarding process—though higher-status passengers still board first. That means more passengers have to make room to allow others to get to their seats, which tends to slow down the process.

Other airlines have come to the conclusion that those few minutes of efficiency are simply not worth it.

“The biggest obstacle is simply the unpredictability of human behavior,” said Greg Forbes, managing director of airport experience at Delta Air Lines.

In theory, Forbes believes Delta could probably shave a few more minutes off boarding time on its planes. But he says these complicated plans don’t always work in reality: Passengers arrive late, have a lot of carry-on luggage and sometimes board in the wrong order.

“All of these things would probably save a minute or two, but you’d lose time again the moment someone forgot their headphones in their bag or had trouble getting a bag into the overhead bin,” Forbes said. “I think that last minute optimization would come at the expense of consistency, reliability and stress.”

It is not yet clear how Southwest will handle seat assignment. The airline plans to provide further details at an investor event on Thursday.

Southwest Airlines flights are listed on a departure board at Chicago’s Midway Airport. For the first time in 50 years, the airline is deviating from its open seating policy and moving to assigned seating.

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Former Southwest employee Doug Lawson says the company hasn’t told him what it plans to do. Lawson, who now works as a consultant, says the end of open seating surprised him. It’s still faster than many onboarding strategies, he says, because it tries to accommodate human behavior rather than fight against it.

“If you think about it, that’s why empty seats are so popular. People don’t want to sit in the middle seat. So it’s almost never the case that two people get up to make room for someone,” Lawson said. “So you’re taking advantage of people’s behavior, right?”

Open seating was once a critical part of Southwest’s financial success, says Jody Hoffer Gittell, a professor at Brandeis University and author of The path of Southwest AirlinesHowever, for it to work, the cooperation of the airline’s passengers was always necessary.

“Passengers may not be as willing to cooperate in finding a seat. This ability to motivate passengers to self-organize was really critical to this strategy,” Gittell said.

In fact, some long-time Southwest customers complain that other passengers take advantage of the open seat system by boarding early and reserving seats.

Gittell suspects that the open seating arrangement simply does not work so well in a deeply divided society.

“It might be difficult to orchestrate that kind of good-natured ‘Let’s go in there quickly, I’ll take this seat and you take that seat,'” she said. “It’s a collaboration and a co-production of the clients that makes that possible. And pulling that off in our culture today could be challenging.”