Another point right there, the conditions don't seem very fixed, not just regarding weight, but in general.
The period I mentioned a few years ago when they had some fuss about over-sized passengers, they never made it clear exactly what was over-sized. As I noted, the man in the news that AA was saying needed to purchase a second seat to return home had flown the same airline on his way out without a complaint from the airline.
You can't play by the rules when the rules are continuously in flux.
....it is incumbent on YOU to look at and understand those terms. Yeah, right, while legally that is definitely true, how many can truly understand the legalese doublespeak of terms? It can be almost as bad as an EULA.
As far as can I fit in one seat, define fit. The seats are extremely narrow. While I can fit between the armrests, my shoulders are wide enough that they are certainly not going to be 100% within the edges of the back of the seat.
And yes, I'm overweight also. I'm sure many would prefer not to sit next to me. However, on the notion of preferring not to sit next to me, does the airlines spell out other conditions that one intrudes on one's seatmates?
Let's see; body odor, alcohol rowdiness, constant up and down for something overhead, kicking the back of the seat in front, shifting feet constantly and bumping their neighbor's. Granted, knee/leg room is almost nonexistence, those tall people someone mention as being less of a problem than fat people normally have their knees pressed into the seatback in front of them.
You have to deal with reality flying. Airlines have to be profitable. And I like lower rates as much as anyone. The question becomes when do you pack another body in to make costs at the current rates? Maybe we should be like those far east shuttle flights I saw a news broadcast about? they had them standing in the aisle holding on to straps like a subway car.