Panoramic cabin view onboard an ANA 787-800 Dreamliner

Optimal Boarding Method for Airline Passengers (Jason H. Steffen)

Speaking of “Old Dog, New Tricks,” I’ve been thinking about other problems that airlines could very well tackle without physically changing anything about their aircraft or equipment. One of these is the classic boarding nightmare that we’ve all experienced – waiting for what seems like a lifetime just to get to your seat, because everyone needs to lift their hand luggage into the overhead bins. I read an article in the Washington Post by Jason H. Steffen, a professor of astrophysics at Northwestern University, who has spent some time studying this problem. Steffen argues that lengthy boarding queues are driven by two factors.

First, the practice by most commercial airlines of charging for checked baggage leads most passengers to maximize (and often times, exceed) their hand baggage allowance. I’m certainly guilty of this – on my most recent trip, I brought a rolling hand-luggage and a duffel bag that didn’t quite fit underneath the seat as per airline guidelines, so I had to spend the time storing both in the overhead space (after all, I need that space under the seat for my legs). Anyways, it’s simple: the more stuff people bring onboard, the more time it takes to store all that stuff and get everyone in their seats.

The second factor driving the problem is the boarding process itself. Most airlines board their passengers in the following way: first class, business class, membership club members (by rank order), and finally economy class. Within the standard boarding procedures for economy class, passengers will board from the back of the plane towards the front. As a result, the majority of passengers get stuck in the aisles, waiting for those who boarded ahead of them to store their luggage and sit down. This causes the painful boarding queues that frequently extend out of the aircraft and onto the jetway. According to Steffen, “the problem is that boarding from the back to the front is a serial process: only one action at a time is completed…The aisle in the airplane isn’t used effectively.” The only other boarding process currently in service is the “industry gold standard of open seating,” pioneered by Southwest Airlines and popularized by other low-cost carriers such as Ryanair. In this model, passengers don’t have assigned seats at all, and boarding time is significantly improved.

In Steffen’s view, “a more efficient way to board would have only as many passengers in the airplane as can put their luggage away without interfering with each other. Those passengers should also be ordered so as to eliminate the need to pass by anyone either in the aisle or in the rows. In other words, it is better to make passenger boarding a parallel process where multiple actions occur simultaneously, instead of a serial process.”

To satisfy my need for excruciating detail and evidence, I read through Steffen’s 2008 research article in the Journal of Air Transport Management. As per the abstract, “Using a Markov Chain Monte Carlo optimization algorithm and a computer simulation, the passenger ordering that minimizes the time required to board an airplane is found.” (I will admit, after reading the abstract, I almost gave up…but then I kept at it).

Here’s a PDF of the research paper: Jason H. Steffen – “Optimal boarding method for airline passengers” – Air Transport Management, 2008

In his research, which is best summarized by his Washington Post article, Steffen builds on the same optimization technique used to answer the famous “Traveling Salesman” problem: given a set of cities and the distances between them, what is the shortest possible route to visit each city exactly once and return to the original city? The resulting Steffen method features an airline boarding procedure whereby “adjacent passengers in line will be seated two rows apart from each other. The first wave of passengers would be, in order, 30A, 28A, 26A, 24A, and so on, starting from the back. (For a typical airplane there would be 12 such waves, one for each seat in a row and for odd and even rows.)”

Steffen conducted a field test of his proposed method versus others, using a mock Boeing 757 fuselage with one aisle, 12 rows of six seats, and 72 passengers. The experimental results show that the Steffen method outperforms current industry practices, with a 2x time advantage over back-to-front boarding, and a 20-30% improvement on random boarding order. Depending on the specific aircraft used, “the optimal boarding strategy may reduce the time required to board an airplane by a factor of four or more.”

Here’s a PDF of the experimental results: Jason H. Steffen – “Experimental test of airplane boarding methods” – Air Transport Management, 2011

The main problem to implementing the Steffen method is getting passengers to line up exactly as prescribed. In Steffen’s own view, the primary benefit of using his method is that “it allows an airline to measure how much room there is for improvement and identifies where that improvement is to be found.” I think that airlines would consider this proposed boarding process (or something similar) if it were framed in the context of the potential cost savings from its use. I recall watching a documentary on Emirates’ ground operations at Dubai International Airport (DXB), where the airline has placed digital clocks in front of every plane at the gate to ensure precision arrivals, turnarounds, and departures. For every second beyond its scheduled departure that a plane remains at the gate, an airline loses thousands of dollars caused by late fines and delays to other aircraft waiting to park. This is a business dominated by intense negotiations between airlines and airports over the use of parking gates and arrival/departure windows. I’m sure that airlines would react positively to the notion of speeding up the boarding and/or turnaround process, if the ultimate result were to allow them to handle several additional flights per day or save on airport gate costs. And passengers would be relieved from the presently aggravating experience of boarding a plane. Sounds like a win-win for all parties involved.

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One comment

  1. Very interesting insights into the boarding process. The system of Steffen sounds really intelligent. Sadly, most airline don’t use any specific boarding process, so it took hours to get onboard.

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