I think Spiff said it best. Assuming the person whose seat is being encroached upon is aware of the rules, following something similar to those suggestions is the course of action to take. It's obvious from the OP, and what happens most of the time, is that nothing will happen if the affected passenger does nothing.

The main problem I see with the whole situation is that a lot of people are going to be reluctant to confront the situation directly, as it will involve confronting the POS and things have the potential of getting nasty. It's easy for all of us to speak here in our positions in front of our keyboards and not actually on board with a POS seatmate.

The way I would look at it is that any uncomfortable situation is ultimately the responsibility of the POS, even if they are the ones most upset. Without assigning any blame to the underlying situation, and without passing judgment, I think it's reasonable to assume that a POS knows ahead of time that they don't fit into a single seat in coach, and by not taking advantage of the advanced accommodation that the airline provides, they have created the on-board confrontation themselves.

I hope that most of the time, it could be handled tactfully such that everyone is accommodated and nobody feels discriminated against, but if it doesn't work out that way, it's ultimately the responsibility of the POS (for not taking advantage of the several opportunities provided to address it before the on-board encounter, not because they're responsible for being a POS). If I were the passenger that had only a partial seat, pushed the matter, and the POS got very upset, I'd probably feel terrible about it, but I think I'd re-assure myself that it really wasn't my fault for creating the confrontation.

I think that's why the OP asked about the policy, to avoid confrontation. Most people don't like confrontation, and if policy was that they were not allowed to encroach on neighbor's seat, then the FA should have done something. Of course, we know the FAs are extremely busy so it doesn't happen, or that it's just not policy.

I think that the OP was a stand-by passenger (if not consider the case of a stand-by). If that is the case, he is the one that might have been left off the flight (no room to accommodate stand-bys)

One doesn't have to confront the POS. Simply do not sit down (or get up) and go right to the FA/Purser. They are paid to sort these matters out, or at the very least summon the GA to sort it out. There's no need to say one word to the POS, unless one thinks one can be ok if the armrest is lowered. Otherwise, just go see the onboard leader. It's their job, even if they won't volunteer to assist at first.

Any standby passengers will be deplaned to accommodate confirmed passengers. If one is a standby passenger and there's only a fraction of a seat left, then the standby can lump it or take the next available flight.

I didn't say confront the POS - I said "confront the situation." I actually meant what you suggest below:

My comment still stands: Many people are going to be reluctant to confront the situation, even if it involves not dealing with the POS directly and just dealing with the FA/GA.

I see now and I agree, most people don't like confrontation.

That makes it more lucrative for those of us who don't mind confrontation... (buying a car, e.g. ;) )

Good advice. I see no reason to discuss the matter with the oversize seatmate; let the crew or GA sort it out. Moreover, I think this is the polite way to handle it as you never know exactly why someone is large. The only thing I'd add is that it probably pays off here to be polite to the crew in asking for help. Going up and demanding that someone be removed because of size probably isn't the best approach, though one may have to be more insistent if the crew is unresponsive.

+1. It is really the airline's responsibility to handle the situation according to AA policy–ideally the FA/GA/purser, as a knowledgeable professional trained in customer service, can approach the POS of in a nondiscriminatory and non-embarrassing matter, and reseat or re-accommodate everyone in a civilized fashion.

Attempting to directly confront the POS probably isn't a good idea–while some people may make a fuss regardless, in general they will probably be less threatened, less embarrassed, and more accommodating when approached by an official AA representative than by a random passenger.

Of course, not every AA employee is the epitome of customer service professionalism, and not every passenger is reasonable either, but when possible, it seems that asking the crew to handle the situation is the best alternative.

And congratulations to us for managing 4 pages and counting with an unlocked thread on this topic! Maybe the AA forum is actually getting more responsible in 2011.

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I think it is also appropriate to remember that there some people who are certainly not 'overweight' as per the thread title, but still do not fit into a standard seat width.

I was on a flight last year where a number of competitive body-builders were travelling to an event. I defy anyone to describe them as 'over-weight' yet most stood no chance of fitting in due to width rather than girth.

So let's remember that this problem affects more people than we might imagine and remind everyone who for one reason or another cannot be properly accomodated in the seat they have booked that the time to deal with this is before the flight, not during boarding.

I've been in that situation: flying LHR-ORD-BOS*, stuck at ORD because of a winter storm, no more Boston flights leaving that day, exactly one took off the next day. There was one seat available on it. As EXP at the time (and dating an EXP desk agent, which may not have hurt) I got it. It was a middle seat in the rear of economy ("Upgrade? Sir, do you want to leave Chicago today?") next to a chap on the aisle side who couldn't lower the armrest. He was aware of his size, made himself as small as possible, but that wasn't really "small." It wasn't the most comfortable three hours I've ever spent on a plane, but I was sure glad to be there!

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*For the miles, natch.

This is not true. If the POS did not purchase the second seat that they are partially occupying (see official policy posted upthread) then a standby passenger will not be displaced to accommodate them. According to the manifest there is a whole seat available. If the confirmed POS agrees to pay for the additional seat (assuming they hadn't done so ahead of time) then it is probable (and I believe, protocol) that they will get priority for the seat over a standby passenger. The POS pays the same rate for the seat as their original seat, so it may be significantly less than the current available price. Bottom line: a confirmed passenger has priority for a seat they purchased over a standby passenger, but a confirmed passenger does not have priority for a seat they did not purchase.

that's not how I read AA's POS policy. Once a standby pax is cleared, they become a "passenger" and are entitled to their full 17" of seat width, not just "whatever fraction of a seat is left". When the cleared standby arrives to see less than 17" available, that would be be the time to inform the crew to apply AA's POS policy, which means that the POS would be reseated to a space with a seat with an empty seat adjacent if available, an empty F seat (not likely at boarding), or be deplaned and given the opportunity to purchase a second seat on a later flight.

When GAs clear standbys, I've never heard them say "I've got 13" of seat if anyone want to go to XXX, take it or lump it"

No argument from me that "confirmed" should mean confirmed, but I can only imagine that the GA will "unconfirm" a standby in such a case and let said standby sort it out with customer service instead of trying to get the POS to buy that second seat and/or offload the POS.

In which case it technically becomes a case of IDB, and the previously-standby-then-confirmed-now-unconfirmed pax should request the DOT-mandated compensation.

Still no argument from me.

However, "confirmed" standbys get offloaded all the time for late-arriving passengers and "confirmed" upgrades sometimes get downgraded when a passenger makes his/her connection unexpectedly. I'm not saying that any of these situations should happen, but in all of them, the passenger will usually have to seek compensation after the fact.