United Airlines is re-introducing its WILMA window-to-aisle boarding process, which the airline says saves an average of two minutes per flight. This is not an insignificant savings. Ground time costs airlines an estimated $100 a minute. A $200 savings per flight, multiplied over the 4,900 daily flights the airline operates, means nearly a million dollars in daily savings.
But is this boarding process the most efficient? Experts have conducted multiple studies to find the optimal boarding processes, and their findings differ.
Airlines Seek Efficient Aircraft Turnaround
Efficiency in the aviation industry is crucial for both airlines and passengers. Passengers want a seamless, stress-free boarding experience, while airlines need to minimize costly aircraft turnaround times to keep flights profitable. A recent study into average aircraft turnaround times at airlines worldwide found room for improvement. It was conducted by technology firm Assaia, which has developed Apron-AI, an aircraft turn optimization platform for the aviation industry.
The Assaia study looked at nearly 150,000 aircraft turnarounds at around 100 gates. It covered over 25 airlines at ten airports on three continents and 101 aircraft types. The study only considered turnarounds that up to 300 minutes. That is the cut-off point when the operation changes from a turnaround to where the aircraft is parked awaiting its next flight. The study only looked at short- and medium-haul narrowbody aircraft operations because those are the most time-sensitive.
The study groups’ average turnaround times range from 107 to 66 minutes. The average ground delays vary between eight minutes for the best performers to 26 minutes for the worst. The average ground delay can be made up by making turnarounds more efficient, such as improving the passenger boarding process.
The two minutes United saves boarding can also avoid flight cancellations. Delays have a watershed effect on the entire aviation network. The eighteen minutes difference between Assaia’s study’s best and worst performers adds up to an hour and a half over five flight segments daily. The cumulative delays can result in the last flight out being cancelled, particularly at airports with time restrictions.
The Quest For The Best Way To Board A Plane
There have been numerous studies trying to find the best boarding process. Study results have examined the impact of different boarding methods on turnaround times, airline costs, and overall passenger satisfaction. Their views differ. United Airlines’ new boarding system, window-to-aisle, also known as WILMA or outside-in, has performed well on various models.
Random Seating
Some studies suggest that random seating, which low-cost carriers Southwest Airlines
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Back-To-Front
Because it is easier to implement, the most common strategy is back-to-front. The plane’s last row is the first to board in this case. All rows are seated before the front rows get to board. Some airlines simplify back-to-front boarding by calling for blocks of people to board back to front.
Outside-In
United’s outside-in boarding or WILMA boards window seats first, followed by middle-seat passengers and aisle seats. It saves time in two ways. Since everyone is seated in separate rows, they are not asking other passengers to move seats. When storing hand luggage, they do not interfere with each other.
Reverse Pyramid
The Reverse Pyramid combines back-to-front and outside-in approaches. It was developed by America West Airlines and Arizona State University. The first passengers to board are in back window seats, followed by window seats in the center and front. Then middle seats in the same order. Aisle seats at the front are the last passengers to board.
Block Boarding
Some airlines board their planes in blocks or zones. In this case, there are several boarding zones on the airplane. First, passengers are boarded in zone 1 of the aircraft, the last rows. The front rows, zone 2, are next to board the plane. In the center, the order is repeated, starting with the furthest unoccupied rows and moving toward the front.
Steffen Boarding
Astrophysicist Jason Steffen developed the eponymous Steffen boarding strategy in 2008. In Steffen’s strategy, passengers are called one by one to board. Boarding is still based on outside in, windows to aisles. To avoid crowding, passengers board two rows apart. Though theoretically the most effective method for boarding, it is not practical. Gate agents have more work, and families and couples sitting together may not want to leave someone behind.
Modified Optimal
Modified optimal boarding divides passengers into four groups and boards them in alternating rows. Passengers in even rows on one side of the plane make up the first group. Next are the passengers on the other side of the plane, sitting in even rows. The process repeats for odd rows.
Reverse Pyramid For The Win
A recent mathematical analysis found that the America West Reverse Pyramid is the second most efficient boarding strategy, except for the theoretical Steffens strategy. Block strategy performed worst overall. Reverse Pyramid ranked 11% better than random seating when 75% of passengers brought hand luggage. A reverse pyramid improves efficiency by 16% over a block strategy. Using the reverse pyramid is also better when all passengers carry hand luggage. In that case, it is 15% faster than random and 21% faster than block seating.
Supporting that efficiency, the reverse pyramid also has the advantage of less contact between passengers. But overall, this study validates United Airlines returning to WILMA. The mathematical model found that WILMA results in an average boarding time of well under 15 minutes.
Despite the headlines, window-to-aisle boarding isn’t new to United. A study by the Hamburg University of Applied Sciences, conducted in 2009, previously determined that the window-to-aisle boarding strategy which United Airlines used then performed best.
Bingo Boarding
In 2019, easyJet and Gatwick Airport trialed a hybrid method called bingo boarding. It was a variation of the reverse pyramid strategy, combining back-to-front and outside-in. It also adopted an element of the Steffens strategy. A gate screen display showed the seat numbers as they were called to board the plane. This boarding strategy resulted in a 10% reduction in boarding time. But their 14-minute average is still higher than the United Airlines WILMA approach.
Balancing Earnings With Better Boarding
Airlines must avoid forfeiting the ancillary gains from preferential treatment when designing their boarding strategies. United is preserving its preferential boarding to accommodate passengers and preserve the value of its loyalty programs.
Low-cost carriers have also recognized the ancillary benefits of separate boarding, offering boarding priority and seat selection.
Southwest, which has used a random boarding process without seat assignments for decades, has embraced the earnings potential of customer preference. Ancillary experts IdeaWorksCompany estimate Southwest generated $750 million from its Early Bird Check-In and Upgraded Boarding services during 2022.
JetBlue reported revenue from passenger transport-related activities of $582,240,000 in 2022, according to the IdeaWorksCompany and Car Trawler ancillary yearbook. This figure includes onboard sales such as food, beverage, entertainment, and other perks the airline offers. IdeaWorksCompany believes JetBlue includes fees for assigned seating in this category.
Spirit reported non-fare revenues of $2,533,548,000 in 2022 from ancillaries, including bags, seat selection, and other travel-related fees.
The Environmental Benefits Of Better Boarding
Today’s airline industry is focused on operational efficiency, profitability, and sustainability. The time an aircraft spends at the gate directly affects its carbon emissions. Therefore, any improvements in boarding efficiency can positively impact the environment by reducing the energy consumption of aircraft on the ground. According to the Assaia study of aircraft turnaround times, the worst-performing airlines ran their auxiliary power units for 16 minutes longer.
The average APU consumes 1.7kg of fuel per minute. The result is an additional 27.2kg of fuel burn. Thus, the additional APU usage generates 85.96kg of emissions. After aircraft taxiing, it’s the second most significant source of greenhouse gas emissions during an aircraft turnaround.
As a whole, the aviation industry is moving toward sustainable practices. Flight routes are optimized to reduce fuel consumption wherever possible. Airlines are buying more fuel-efficient aircraft. Efficient ground operations, including better boarding processes, are essential to these sustainability efforts.
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