SteveinSTL

I too have had similar story (singular, no need to elaborate, others have clearly told the gist of it). My feeling after talking with a FA on the subject was that passengers are renting space to go from point A to B in various stages of service. We are renting a cube of rectangular airspace, and it is the airline's job to get us there in a reasonable timeframe. If a passenger goes over their space, they are actually in 2 (or in the case of the OP, 3) spaces, and should pay for such. If they were in the shipping business, you could not overflow one container into another without expecting to pay. Neither should you here.

On one sympathetic note to GA's & FA's. Imagine the worst possible scenario of delayed flights, airline problems, and at last minute on a fully sold out flight these 400+ lb passengers appear. Is this the type of argument you relish to have telling them they exceed the space they purchased? It's not pretty, will be seen as not PC, but it's still needed. They can't ride a roller coaster at Disney if they can't get the safety restraint to fit, we can't put bags under the seat if they don't fit, why are morbidly obese customers any different? It's not discrimination; it's simply a requirement of passage to fit within the cube. "Unfortunately sir/madam, we won't be able to accomodate you on this flight as we will need you to purchase 2/3 seats to safely seat you. We have a flight later on that we can do this for you."