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Related to this question about plane loading efficiency, if planes have multiple entrances (generally 6 or more) why are planes not loaded from both ends? I think I've seen it happen sometimes, but the majority of my flights are on 737s and are just loaded from the front entrance.

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    $\begingroup$ Sometimes planes are loaded from both ends. Burbank Airport has no jetways and stairs are usually placed at both the front and back of the aircraft (they have wheelchair lifts for passengers who need them). JetBlue sometimes does this elsewhere as well. At most airports with jetways, boarding occurs from at least the second floor of the terminal building. That means that passengers who take stairs down from a rear exit would have to climb back up into the terminal, which is inconvenient. $\endgroup$ – Zach Lipton Feb 2 '15 at 3:45
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    $\begingroup$ It's also fairly common to have two sets of stairs when aircraft are parked at remote stands and passengers are bussed to/from the terminal (more common in Europe and Asia, generally rare in the US). $\endgroup$ – Zach Lipton Feb 2 '15 at 3:49
  • $\begingroup$ As an aside, for double-aisle and multi-level aircraft, it's common for them to be boarded via 2 or even 3 jetways. When 2 jetways are used, they're usually attached to the 1st and 2nd left-side boarding doors on the first level. When three are used, it's usually those two plus a door on the second level. Getting a jetway around the wing is not practical though, which is the main reason why aircraft boarded from jetways usually don't load from the back. $\endgroup$ – reirab Feb 2 '15 at 14:43
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    $\begingroup$ A related question appears to be why planes aren't loaded from the middle. The real bottleneck isn't the single jetway, it's the crowded aisles. If you had a door just in front of the wing, up to a third of the passengers could move forwards. $\endgroup$ – MSalters Feb 2 '15 at 21:06
  • $\begingroup$ JetBlue at LGB also boards and deplanes in the front and back. Whenever I fly there, I try to book one of the last seats on the plane. Everyone is always so pleasantly surprised that they aren't going to be the last people on the plane! Consequently, there is always a little bit of confusion in the back of the plane, especially when people have put their luggage closer to the front. $\endgroup$ – Trevor Feb 2 '15 at 23:44
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The aviation industry is already running at near-peak efficiency, performing crucial tasks simultaneously to ensure quick turn-around. Trying to speed up the boarding process by allowing entrance from both ends would be doable with a large amount of changes to the existing process, in both operations and infrastructure. However, the result would be horrendous and time- and resource-consuming at worst and comical at best.

  1. Jetways need to be able to reach all points of ingress/egress, where currently, they only reach the forward doors. Seeing as aircraft nose-in at the gate, to reach the aft doors would require a jetway that goes around the wing (above the wing is even less practical from a design/physics standpoint), effectively creating an even smaller limit to the size of the aircraft that can fit at the terminal since there is now a jetway that needs to reach the rear doors. As you can see, the space between aircraft is already tight: aft-capable jetwayOr, you use a simple stairway at the aft door and allow passengers on the tarmac, an already busy place during aircraft turn-around, and we don't need them touching anything en route. I highly recommend against the latter.

  2. In many instances, during boarding, the rear and/or opposite-side doors are already in use for loading/unloading food and drinks and taking out the trash. So you'd have to redesign that process.

  3. Humans are generally stupid in large groups. Southwest notwithstanding, your typical airline assigns seats. Imagine a passenger entering the rear door with seat 1A. It doesn't have to be that extreme. It can be any seat assignment more forward than another passenger coming the opposite direction down the aisle, which has the effect of halting both directions of travel. Passengers already sit in the wrong seats, or travel with babies, or carry too much luggage (or stow it selfishly).

There have been many studies on efficient boarding methods. The most efficient algorithm seems to be the Steffen Method, but this method requires someone with an inordinate attention to detail (and willing passengers) to line people up in a specific order. Taking into account crew resources, the most efficient method is by window-middle-aisle groups, then by random order (i.e. "single-zone"), with typical "zone boarding" least efficient.

EDIT:

There are scenarios where boarding from both ends makes sense and is feasible, e.g. smaller planes with fewer passengers. On larger aircraft, the problem compounds itself as the number of passengers grows, each "collision" incident affecting that many more people in the queue. Minimizing collisions requires airlines to throw more resources at the problem, namely personnel to direct traffic. Ask any CFO - more often than not, human resources is the most significant slice of the operating budget.

In any case, engineering a solution should not entail best-case scenarios; it should be designed for typical-case at best, and more commonly for worst-case. The human factor is one that cannot be overlooked. There is no such thing as an idiot-proof system.

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    $\begingroup$ cost-prohibitive. digging up the ground (tunneling) is monumentally more expensive than building a bridge. $\endgroup$ – Erich Feb 2 '15 at 6:07
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    $\begingroup$ what you describe is a perfect scenario. someone will board from the wrong door. $\endgroup$ – Erich Feb 2 '15 at 9:58
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    $\begingroup$ I have often seen boarding happening from both ends, front and back on smaller aircraft's at airports with bus boarding. Usually security at the front will allow in only rows 1-15 and at the back 16 onwards. (they will stop you before you climb the stairs) $\endgroup$ – Akash Feb 2 '15 at 11:29
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    $\begingroup$ @immibis People in the rear boarding from the front door will cause headaches. Suppose the aircraft has 30 rows and I'm sitting in 23C. I head to the rear door and board from there. Another passenger in 28F has boarded via the front door. We're standing in the aisle blocking each other, and passing in a narrow aisle when we both have roller bags is challenging at best. Meanwhile everyone else is stuck in both directions. $\endgroup$ – Zach Lipton Feb 2 '15 at 23:41
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    $\begingroup$ It's worth noting that while the rest of the operations on the tarmac and at the terminal may be near "peak efficiency" the process of boarding the aircraft is empirically about as inefficient as we can make it (see here from Bloomberg Business, this delightful Mythbusters segment). $\endgroup$ – voretaq7 Feb 3 '15 at 1:56
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I'm not sure, but I think this is somewhat a geometry thing. If planes are being loaded from a jetbridge, it would have to get past the wing to reach the rear door. That would involve it having to drive around the wing to get to the door, which is somewhat space-intensive, and also requires a pretty long jetway with limited ability to have supports along its length (since it has to deal with different wing sizes). On planes with multiple front doors along one side, it's not that uncommon to see them being used, whether they're on different levels or there's just a door at the front and another door in front of the wing. There, it's just a matter of how many jetways the airport has at the gate, but they don't have to drive around the wing.

When planes are being loaded or unloaded away from the airport, it's not uncommon to load/unload from the back as well as the front; there, they just have to use two mobile lounges (at IAD) or airstairs (just about anywhere else).

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  • $\begingroup$ This is the primary answer. We like jetways and getting a jetway around the wing is not feasible while parking aircraft perpendicular to the terminal. Parking parallel to the terminal would both be difficult to maneuver and take up too much space per aircraft. If you want a really good idea of how dense aircraft parking at terminals can be, take a look at Atlanta. $\endgroup$ – reirab Feb 2 '15 at 14:38
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    $\begingroup$ Atlanta should never be used as an example, on account of the fact it's an inherently silly airport with an underground train. The sooner Hartsfield-Jackson accepts that it's a theme park, not an airport, the better. $\endgroup$ – Jon Story Feb 2 '15 at 16:40
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Some lowcost airlines use both ends to speed up both loading and unloading the passengers. Moreover, for huge aircrafts (A380 and B747), you may use several jetways

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    $\begingroup$ This is common for Ryanair in Europe. $\endgroup$ – UncleZeiv Feb 2 '15 at 14:25
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    $\begingroup$ It's very common for most European low-cost airlines. $\endgroup$ – Jon Story Feb 2 '15 at 14:51
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    $\begingroup$ This is always done with two stairs, (not a jetway and a staircase) and generally away from the terminal building to avoid congestion at the jetways. I suspect that, besides the increased height, larger planes have increased probability of a disabled passenger, which would make stairs not an option. $\endgroup$ – Level River St Feb 2 '15 at 17:35
  • $\begingroup$ @steveverrill Yes, having more passengers increases the probability that you have one who can't use stairs. But boarding by stairs is, as Jon Story says, very common for European budget airlines and they must have some method of getting people who can't use stairs onto the plane. $\endgroup$ – David Richerby Feb 2 '15 at 18:38
  • $\begingroup$ @steveverrill: as a side note I had a few cases where the passengers were leaving the plane via the jetway and stairs (and meeting at the top of the tower - the stairs ones needed to climb up) $\endgroup$ – WoJ Feb 3 '15 at 12:08

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