# It’s time to fix how we board airplanes

I travel often enough that when people ask me where I’m based, I sometimes joke “Seat 4F.”

I’ve been able to observe a lot of passengers boarding planes. Based on what I’ve seen, how we board airplanes doesn’t work very well. And based on what I’ve read, it doesn’t make sense either.

All U.S. airlines allow first class, business class, and their most frequent flyers to board before everyone else. In addition, some airlines sell priority boarding for an additional fee. Most airlines board everyone else in the same way: passengers sitting in the very back board first, with more passengers allowed on the plane gradually from back to front.

Monte Carlo simulations have shown this is an inefficient method. Mathematically, whenever a passenger tries to sit down, there’s a 1 in 3 chance that someone will already be seated in that row and have to get up to let the new passenger in – this slows things down. In addition, most of the people boarding are around the same rows and trying to use the same overhead bins so there is lots of congestion in the aisle. This video simulation shows the congestion well:

United Airlines uses an outside-in boarding process which allows everyone with window seats to board first, regardless of row. After that, all people with middle seats board and then all people with aisle seats. United refers to this as “WilMA” (Window, Middle, Aisle).

An episode of Mythbusters showed this process is nearly 50% better than the more common back-to-front because it reduced congestion in the aisles. The downside of outside-in is that passengers sitting together can’t board at the same time. This could be a problem for families with young children which is likely why United allows them to board earlier.

Outside-in is faster than back-to-front but the unassigned seat method used by Southwest Airlines is even faster (but not by much). Passengers board in order of check-in but, since they have no assigned seat, can sit wherever they like. People naturally avoid congestion and navigate to open rows. While the unassigned seat method is slightly faster than outside-in, it leads to lower customer satisfaction scores. Many people, including me, like to know where they are going to sit before they board – especially if they are traveling with others.

The best boarding method might be a debate between outside-in and unassigned seat assignments if not for a physicist named Jason Steffen. Steffen’s method essentially combines outside-in and back-to-front; instead of window seat passengers boarding in any order they want, they board back to front. After window seats, middle and then inside seat passengers board back to front. An episode of the PBS series Making Stuff Faster tested the Steffen method as 25% faster than Southwest’s unassigned seat technique – making it the fastest known method.

There are three boarding techniques which are all significantly faster than the commonly used back-to-front method. So why don’t the airlines switch? It could be nothing more than an unwillingness to change. Or maybe it’s because more and more passengers are paying an additional fee to board early.

What do you think?

This blog was originally posted on Manage by Walking Around on February 12, 2017.

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Interesting post which many travelling consultants I'm sure have lots of opinions...But as modelling always requires the right inputs to get the right optimisation, I thought I'd add the following thoughts:

Luckily I haven't had to do the weekly commute on the plane for quite a few months; but the one thing I note makes the biggest difference is limiting cabin baggage. In Australia, we have some airlines that force a limit of 7kg which smooths out the boarding no-end (except for those who try to carry more); but in America, I see people with more like 20kg suitcases which is crazy and is the main reason in my mind why boarding early is seen as a privilege since you may need to store luggage at the back of the plane, or in some cases, underneath (not to mention waiting for ages as that person tries store their 20kg bag in a space not meant for it)!

Some American airlines I noted offer free checking in of this type of cabin baggage which I think greatly helps; but then for those frequent travelers who just want to get to their taxi from the plane, checking in bags and getting them when you land is probably where we need to focus on for efficiency in boarding as that means we can remove the privilege of boarding first and board efficiently since it won't matter!

BTW - I remember the days that privilege was you got to board as the very last people (staying in the lounges as much as possible), but that was when everyone just checked in bags and airlines were so inefficient themselves!

Cheers,

Matt

Good point, Matt. I'm sure carry-on luggage is one of many significant variables affecting how these models play out in the real world.

As IoT technology proliferates -- and the older factors you mentioned disappear -- I wonder if airlines will be able to incentivize individual passengers to speed up their boarding for the good of everyone on the flight.