…what happens?
Do you have to buy two seats? What if two adjacent seats aren’t available?
Are airlines required to accommodate you in any way?
Are certain airlines known to be more helpful?
Most will require you to buy two seats. Some will refund you the second seat if the plane isn’t full. Airline policies change on almost a daily basis, are inconsistently and arbitrarily enforced, and are almost never published where the general public can view them. You’ll have to check each one individually. Sorry to be not much help.
Most people who cannot fit in a single seat are given a seat-belt extension so that their seat belt can fit them while they sit in their seat and their neighbour’s lap.
The usual policy is to require the passenger to buy a second adjacent seat. Depending on the degree to which the flight is booked, your frequent flyer status, and the mood of the check-in agent, this may be waived, but you can’t count on it. I guess, though, that most passengers who belong to that category don’t buy two seats straightaway; they buy one and wait for the check-in agent to require them to get a second one, hoping, of course, that this doesn’t happen.
Seems that they don’t have to be adjacent:
The real kicker is how they make the seats smaller all the time in order to stuff more people into coach. It’s not going to be long until absolutely normal-size people are “too big” for a seat.
And we all know that prayer we say when we see a huge person coming down the aisle: please, not next to me, please, not next to me, please please please.
Roddy
Speak for yourself! I don’t care about the size of fellow travelers!
Your link didn’t work.
The news reported yesterday that the new standard for coach seats is 17.5 inches. It’s hard to find any chair, outside these airline seats, 17.5 inches.
The reporter, who was actually rather slight, could fit, but not comfortably.
There was a push, (that failed) to make it ok for standing with hand straps on short haul flights.
Let’s see if it’s brought forth again and succeeds.
Try this one. Not sure why taking the URL right off the address bar truncated it.
Just so you all know, Boeing doesn’t decide the seat width, the airline does. Boeing, and I’m sure other airplane manufacturers, design and install to the customers’ specs.
[QUOTE=What the ???]
Are airlines required to accommodate you in any way?
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They are in Canada. The Transport Board ruled that charging extra based on size discriminates based on disability (ie obesity) and that airlines can only charge per person.
In other words, “A person’s a person, no matter how large.” 
From 2009 - http://www.bloomberg.com/apps/news?pid=newsarchive&sid=ajtmQ7v86kyg&refer=home
Additional searching find the phrase “fat flyer,” leads to results.
I don’t either, unless they are spilling over into my seat. I don’t think less of them as a person, believe it or not, but I don’t see why I should be the one to have to accommodate their “disability” by being (even more) uncomfortable for several hours. Flying is bad enough for me (long legs, hips that tend to spasm if left in one position too long) without that.
Roddy
Here’s the thread from 5 years ago discussing the Canadian decision requiring airlines to provide two seats with out an extra charge: Canada Supreme court won’t hear obesity two-for one seating case vs. Air Canada
Having flown on an airliner recently, I can assure you, that time came long ago. 
Like Roderick Femm, I care if it affects me, which it did a few months ago. Fortunately it wasn’t a really long flight but 2 hours is long enough. I always choose aisle seats and the guy next to me (who smelled as well btw) needed a seat belt extension. He somehow got his ass into his seat but the rest of him will spilling over the armrest and had me leaning into the aisle the entire time.
Leaning into the aisle was bad enough but I hate to think of what this would have been like if I was between him and the window.
I don’t think of this as a bigotry issue but, why should I or any other passenger have to be more uncomfortable as a result?
I know that at least one airline (in Samoa) is starting to charge passengers based on a metric of weight and distance. In short, if you bring more weight with you (both your own weight and your luggage’s weight), you will pay more for the flight. If you travel light (whether that means you weigh less, or simply pack less stuff with you) you will pay less.
Actually, I do care about the size of some travellers.
But it’s not the 6 foot tall, 300 pound guy who I dread…it’s the 3-foot tall, 45 lb kid…
The hopper flights between San José de Costa Rica and Liberia (the Costa Rican town, not the African country) include a total weight per person allowance: heavier people can carry less luggage.
If you have too much luggage, you have to leave some behind and ship it. When will it be shipped? Next time the flight’s total weight allowance isn’t reached: if everybody insists on traveling with half their house, it can take a while, but hey, they’ll phone you to let you know your stuff is on the way! My boss was able to ship the server he’d brought (unrelated to work, he wanted it to practice some stuff on it, and don’t ask me why it couldn’t be practiced on a laptop) and a bit of clothing thanks to two of us being under the weight limit; the rest of his clothes came five days later.