United Airlines rolled out a system for boarding economy passengers this week called WILMA, loosely translated to “window-middle-aisle,” which boards window passengers first, followed by the middle and then aisle seats.

The approach is expected to shave minutes off boarding and address one of the most dreaded parts of flying: waiting in lines. 

Every minute counts when boarding and maximizing profits; according to the Los Angeles Times, a 2008 study found an airline could save up to $30 per flight for every minute shaved off boarding time.

In the face of longer boarding times, experts and airlines — and even a beloved TV show — have taken a stab at uncovering the fastest way to get people on the plane. 

“The model that I employ assumes that the time that a passenger requires to load his or her luggage is the dominant contribution to the time needed to completely fill the aircraft,” he said in his 2008 paper.

Passengers are boarded according to WILMA, but in alternating rows, which helps prevent the wait for passengers to put up their luggage and let people into their rows.

However, this method will likely never see the light of day, as it requires extensive coordination from the airline and an unholy number of boarding groups. Passengers would have to line up in a precise order, and families and other groups would be unable to board together.

Most major airlines use boarding groups to seat their passengers on the plane, first prioritizing VIP boarders and then moving on to board the main cabin and economy passengers from back to front. While this makes sense in theory, studies have shown that it’s actually the least effective way to fill a plane. 

Instead of improving efficiency, this method ensures that the line moves from the gates to the jet bridge to the aisle. Passengers have to wait while others load their luggage into the overhead bins and play musical chairs as they let their neighbors into middle or aisle seats. 

A 2014 episode of “MythBusters” found this process took 24 minutes, 29 seconds to board a simulated “average-sized, single-aisle airliner” — that’s a lot of wasted time and was the slowest of the methods the show tested.

Airlines based overseas, like Air France and Ryanair, board passengers in the order they line up. The process is faster because it’s less likely multiple people will try to board in the same rows simultaneously.

The outside-in method, also known as the WILMA method, seats passengers according to their chosen seats. 

This method is even faster than seating at random because more rows can board simultaneously, and there’s no need for passengers in middle or aisle seats to get up and let other passengers into their rows.

United Airlines said it would return to window-middle-aisle seating because it shaved 2 minutes off boarding time in the airline’s tests.

Studies have proved that Southwest Airlines seats its customers the fastest, according to CNN. “MythBusters” also found Southwest’s method the fastest, saying it took only a little over 14 minutes to get passengers to their seats.

Southwest follows the random method but takes it further because its passengers don’t have assigned seats. That gives its process all the benefits of the random method and then some — people spend less time waiting in the aisle because they can plop down into any available seat.

Another reason Southwest boarding goes faster is that the company allows two free checked bags per passenger. This gives customers an incentive to bring less carry-on luggage and get into their seats quicker.

While the Southwest method may be the fastest way to board, the airline isn’t immune to trying to bribe its customers into upgrades. Frequent flyers are awarded priority boarding, and others can purchase priority boarding for a fee. 

Southwest has also been testing methods to get customers boarding even faster. This year, the company has tried add-ons like upbeat music to get passengers grooving down the jet bridge and video monitors that provide visual cues for boarding. Back-office tests include a group chat for workers on the ground, on the plane and at the gate for faster communication.

“If we spot stuff that works and it can work stand-alone, we will roll that out,” Andrew Watterson, Southwest’s chief operating officer, told the Wall Street Journal. “But we’re not looking for all quickies. At the end of this, we want to get our turn times down five minutes and have it be in a quality, customer-friendly way.”