Thursday, May 01, 2014

How to Board an Airplane

I've just read an article on different ways of getting passengers onto an airplane, arguing that South-western's current method is the best of those used, although there is at least one alternative that is better still. The article did not consider the method that has long struck me as the obvious solution to the problem—and that no airline, so far as I know, uses.

South-western lines up passengers in an order mainly determined by when they checked in, then lets them choose their own seats as they board. My method uses the same mechanics—lining passengers up in a predetermined order—but in what should be a much more efficient way.  Instead of lining them up by priority, line them up by seat number. The first two people in line are the ones in the window seat of the last row. The next two are in the window seat of the next row forward, and so on to the window seats of the first row. Next come the two in the middle seats ordered in the same way, then finally those in the aisle seats. 

The advantage seems obvious—since passengers go on in the order of their seats, nobody ever has to wait for a passenger in front of him in line but seated ahead of him. Since the rows fill from the window in, nobody has to wait for someone in his row to get out before he can get in. One might argue that passengers will be unwilling to go along with such an elaborate arrangement—but the mechanics are exactly the same as way South-western does now. The only difference is that the order actually serves a function.

What am I missing? Why don't the airlines do it that way?


At 5:02 PM, May 01, 2014, Blogger machete said...

People, especially families with children, like to (need to) stick together with their traveling companions as they board.

I'm sure a variation of your method, with the additional caveat of skipping rows, can accommodate this.

At 5:09 PM, May 01, 2014, Blogger Unknown said...

Not to be overly pedantic, but it's Southwest, not South-western.

I think the reason that boarding doesn't go outside-rear to inside-forward is because with the introduction of bag fees for checked baggage, overhead bin space is at a premium and it would advantage window seat holders with first choice of overhead bin space.

At 5:09 PM, May 01, 2014, Anonymous Barcelona's Singing Organ-Grinder said...

For unter-budget players like Ryanair: on the one hand, chaos encourages passengers to pay extra for first-wave boarding; on the other, aggressive gate-side shepherding ensures they're always ready when the tower looks up from its whatsapp and grunts yay.

At 5:22 PM, May 01, 2014, Blogger jdgalt said...

I see two potential problems with it.

First, your scheme requires that all seats have been assigned before boarding. Neither Southwest's staff nor many of its passengers are going to be willing to take the time to do so.

Second, your scheme assumes that each passenger will obediently go straight to his seat and sit in it. This assumption breaks down as soon as somebody wants to put luggage in an overhead compartment, or go to the restroom.

(For what it's worth, I have refused to fly since 9/11, because of the TSA. We need to campaign more actively -- or maybe go to court -- to get them abolished.)

At 5:57 PM, May 01, 2014, Blogger Streetwise Professor said...

There is also the fact that some people arrive after the boarding process has started. Your system would work great if everyone is there before the boarding process begins. But late arrivals disrupt the order that your system relies upon.

At 6:24 PM, May 01, 2014, Blogger geogavino said...

Like some have noted, there are many variables that will alter the efficacy of this method. All of them together will make the process much more chaotic than what you describe. Many airlines have used a modified form of this - where they seat a series of rows at a time, starting with the rear. It would seem that this would reduce those variables. I'm guessing this was modified from the arrangement you propose.

The military uses such schemes, but they are able to control everyone's actions leading up to boarding and penalize deviation. Everyone files in and sits in the farthest space available from the door. I always tried to situate myself so that I wasn't in the narrow portions where my legs would have to interlock with the person across. Sometimes they got volunteers to load bags who then got to choose seats.

I've often wondered why they don't have double gangways, where the airport allows, and utilize two doors for large planes.

At 10:54 PM, May 01, 2014, Anonymous Anonymous said...

Air canada actually does board that way, not in a strict order but they will board the back 20% first,.

At 11:25 PM, May 01, 2014, Blogger Unknown said...

Air New Zealand and Qantas use a similar boarding pattern. Rows 50 - 70 first. Then 30 - 50 et seq.

At 11:47 PM, May 01, 2014, Anonymous Anonymous said...

I recently flew Southwest and the process seemed highly inefficient to me. You would think that letting people choose their seats would lead to efficiency but you would be wrong. People's first choice of seats is in the front of the airplane. It would work if they simply sat down and let everyone else through, but that's not how it works. They fiddle with their luggage and try to get it into the overhead compartment, holding everyone up. It doesn't work. Your method of seating the window seats and in the back of the airplane first seems like the optimal to me.

At 1:39 AM, May 02, 2014, Anonymous haakonsk said...

Passengers could be seated in roughly the order you describe, but how about assigning their seats just before they board the plane instead of at check-in or before?

The first two in line would get the back window seats and so on.

If several people are traveling together, they could say how many they are and be seated next to each other.

At 3:08 AM, May 02, 2014, Anonymous Rebecca Friedman said...

1) Sometimes people need to sit together (most often, families with children) - a weakness in Southwest's system, which assigned seating usually doesn't have (or has less) since you can select your seat in advance/change seats if necessary. Assigning seats late would put that weakness back in. Not for the first people in line, who can sit together just fine by your system, but for the people who aren't first in line.

2) Go to the restroom during boarding?! Ah... no. People really do not do that, or at least I've never observed it. They've generally had lots and lots of time before boarding to do that in; if they didn't do it then, they can probably wait until everyone's in their seats. I don't know if onboard restrooms are even open during boarding.

3) Boarding in sets of rows is a standard system (is, to my knowledge, the standard non-Southwest system, and was the standard system pre-Southwest) but is only so efficient; it does mean you don't have people stopping 30 rows ahead of you to get into their seats, but you do have people stopping 5-10 rows ahead, and you have middle/aisle seats filling before windows not uncommonly, with the requisite shuffling when the person with the window seat shows up. So I really don't think it's equivalent to the system being suggested here.

At 5:22 AM, May 02, 2014, Anonymous Sieben said...

uhh I thought that airlines actually did something like this. They don't line you up *exactly* by seat number, but I recall that they essentially said: "boarding rows x-y (in the back of the plane) now", and proceeded in ~3 waves to fill the plane roughly from back to front.

I haven't flown in years though.

At 6:36 AM, May 02, 2014, Anonymous Handle said...

There are three major problems.

1. Airlines make a lot of extra money selling priority boarding as a perk. The optimal strategy may be one that actually chooses a slightly slower boarding process that allows for more price-discriminates and market segmentation, so they can squeeze a little more consumer surplus out of those willing to pay more. If you make boarding slightly longer, there is now more utility to preferential boarding, for which you can charge.

2. First and business class likes to board first and second, and also get off the the plane first and second, but there is only one door.

3. In my experiences, the majority of the jam is due to the issue of non-enforcement of overhead bag discipline. Too many bags, which are also too big. I was on an Air New Zealand flight, and they weighed everyone's overhead bags at ticketing; if it was over 7kg (15 pounds), you had to check it. Fastest boarding process ever, even though it used the typical US-style multi-zone staggered-boarding procedure. It was also a faster security line, since it encouraged people to carry less luggage with them through inspection.

At 7:03 AM, May 02, 2014, Anonymous Anonymous said...

the problem is that you need the passengers to ALL be there and then to sort themselves into the correct order when told to. its extremely unlikely that every passenger would be at the gate when they first open the gate, and its even more unlikely that the time saved by your method would be greater than the time cost of having people sort themselves. also probably no one would want to sort themselves like this.

At 8:07 AM, May 02, 2014, Anonymous Anonymous said...

This is the response that's been going around. I haven't carefully analyzed it against the Voxx piece:

At 8:39 AM, May 02, 2014, Blogger lelnet said...

"Why don't the airlines do it that way?"

Day 1: Hundreds of flights are severely delayed, as children temporarily lost during the process of having them board 15-20 minutes later than the parents flying with them have to be chased down through the airport. Dozens of them will be lost for long enough that their parents give up on the flights, and a handful will be lost at least long enough for Amber Alerts to be posted. Trial lawyers will salivate, and most US airlines will eventually declare bankruptcy (again) when the legal bills finally come due.

Day 7-ish: With exceptions to the boarding policy now in place to allow accompanied minors to board with their parents, agitation begins among childless couples who merely _wish_ to both sit and board together, for a similar exemption.

Day 21-ish: After announcing that men and women wishing to board together need not provide proof of marriage first, the gay activists enter the fray.

Day 30-ish: After announcing that any couple, gay or straight, wishing to board together can do so, business colleagues and friends travelling together begin to inquire as to why the airline should care whether passengers in a group are having sex.

Day 60-ish: Snarky internet people begin posting about how, despite the complex array of new rules and exceptions surrounding boarding an airplane, the de facto process has reverted to what it was before the "windows first, moving forward from the back" change.

At 9:23 AM, May 02, 2014, Blogger jimbino said...

I just flew TAM from Miami to Rio. Brazil. The policy throughout Brazil is to give preference to the disabled, old folks and women either pregnant or with small kids. As elders, we were very surprised to be allowed to board before first and business class and all the others.

I guess your plan wouldn't work with the Brazilian preference system.

At 3:04 PM, May 02, 2014, Anonymous AbsoluteZero said...

A number of commenters have already pointed out the issues. Here are a few points based on my own experience.

Most airlines allow some people or groups to board first, like frequent flyers, senior people, disabled people, families with small children, and so on. Both airlines and passengers want to keep this.

Specifically, families and some other groups need to board together. This is not just a preference. Children cannot board unattended, ahead of their parents or guardians. The adults also cannot board first. There are legal implications.

Boarding from the back of the plane to the front has been a standard for a long time. Some airlines have started to use zones, including from outside in, starting with window seats.

Any scheme that requires all or almost all passengers to be present prior to boarding would not work, as it never happens. Also, some people don't like to sit in the plane and wait, so they want to board as late as possible.

Handle said: "... but there is only one door." This is not necessarily true. While rare in the US, boarding bridges that attach to two doors are not uncommon in Europe or Asia.

I would also like to point out that the airport and the passengers themselves make a very big difference. Efficiency, in terms of how fast boarding is completed, is only one metric. Overall the goal is make the experience positive.

Those interested can go to Skytrax and take a look at their ratings of airlines and airports.
There are only 7 five-star airlines, 6 of them are from Asia, one from Qater. There are only two five-star airports, Hong Kong and Singapore. This is not an accident.

At 5:20 AM, May 03, 2014, Blogger jimbino said...

Families and others who need to board together should pay extra for the extra trouble they cause others.

At 7:30 PM, May 03, 2014, Blogger Patri Friedman said...

None of these points seem very convincing to me. Sure, there are lots of minor ways in which the method is not perfectly efficient. But most of them are minor, or addressable with slight rule tweaks. For example, letting families with children board together at the spot of the frontmost or rearmost ticket would solve that issue while hardly changing the efficiency.

It seems like a small step from Southwest-style to doing it this way. And if people have significant value on assigned seats, it seems a worthwhile one.

At 9:22 PM, May 04, 2014, Blogger Bill Conerly said...

Here's a general rule that I have found useful: do not specify the optimal method of anything until you have determined the objective function.

"Handle" gets to the crux of the matter, which is that airlines are not trying to minimize boarding time.

Most airlines' objective functions tend to include boarding time, but also include rewards for frequent travelers and first class passengers. I think there are other factors involved, but you get the picture.

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At 8:31 AM, May 07, 2014, Blogger J Scheppers said...

It seems to me there are two issues that this method does not seem to address.

First, The methodology establishes two queues. 67% of the time only one person from each queue can be stowing carry-ons or being seated. In the more Hodge-podgy fashion I would think more people are being seated than on average 2 2/3 people at a time.

Second, I question whether loading the passengers is the critical path item to get a plain turned around. My experience is a flight running late all the passengers are seated and the plane is still being loaded with luggage, fuel, or being de-iced or otherwise being resupplied.

It would be easy to measure which currently goes faster de-boarding a plane which uses your method in reverse (due to courtesy). The current de-boarding also has slight advantage that multiple passengers are able to unstow carry-on items while they are in the queue.

The complicating transactions cost that almost all have mentioned in getting everyone lined up also makes this method significantly less desirable.

At 2:18 PM, May 09, 2014, Anonymous John B. in NE said...

You're looking at the wrong end.

People want to get off the airplane quickly; that's why the front seats are preferred. People like not being sandwiched between two strangers, that's why the middle seats fill up last.

Combine those with the luggage space issue and the airline's interest in charging more for 'firstness' and you see why things are as they are.

At 1:50 PM, May 12, 2014, Blogger Thomas Blankenhorn said...

In addition to the points people made before me, I think David is missing a crucial point about baggage.

I have occasionally seen airlines seat their passengers back to front. Whenever this happened, a significant number of backseat passengers would drop their baggage into front-seat compartments, which saved them the trouble of schlepping it up and down the plane. This, in turn, forces the front passengers to walk past their seats, find the first empty baggage compartment, and walk back. The result: chaos, and also a bunch of annoyed front-seat passengers --- who, more likely than not, paid extra to be in first or business class.

At 3:05 PM, May 12, 2014, Anonymous EHutchins said...

Coincidentally, folks at my alma mater recently published a new method of optimizing aircraft boarding. From the website:

Milne-KellySchool of Business Professor R. John Milne and undergraduate student Alexander Kelly ‘14 have devised a method, published this month in the Journal of Air Transport Management, which assigns airline passengers to a specific seat based on the number of bags they carry, causing luggage to be evenly distributed through the plane. Each row of seats would tend to have a passenger with two bags, a passenger with one bag and a passenger with no bags.

The abstract seems to indicate that this method improves upon boarding simply by seat location alone:

We describe a new method to assign seats and to board passengers on an airplane that minimizes the total time to board. Steffen (2008) presents an optimum boarding method that assigns passengers to a specific numerical position in line that depends upon their ticketed seat location. Our method builds upon Steffen by assigning individual passengers to seats based on the amount of luggage they carry. Our heuristic method assigns passengers to seats so that their luggage is distributed evenly throughout the plane. Simulation results indicate that with our method, the total time to board all passengers on a fully loaded airplane is shorter than that of Steffen.

The full article is here.

At 1:42 PM, May 16, 2014, Anonymous macsnafu said...

I may be repeating other people, but it seems to me that maximum efficiency in boarding the plane is just not a high priority with the airlines, and while passengers might grumble a little, it doesn't bother them enough to make loud or insistent complaints about it.

Given all the factors involved, "optimal efficiency" is not necessarily the same as maximum efficiency.

At 3:45 PM, June 01, 2014, Blogger Roman said...

I'd have to agree with one of the commenters in acknowledging that seating passengers is not a priority. Or, to be more precise, it isn't the bottleneck and reason why flights can be delayed.

Delays can occur when passengers are late and they have to unload their bags or wait for that passenger to board and, thus, miss their departure slot. But that can hardly be solved by any kind of elaborate boarding scheme.


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