mrtruman, you are cooking with gas and playing with fire!
THE FAT *ahem* C.O.S. POLICY
The only airline I know with a formal COS (customer of size) policy is SWA. If you do not fit into your seat, and the flight is full, you have to purchase a second seat for half the price of your ticket. If the plane is not full, then I do not think you need to buy the second seat.
The above thread generated quite a bit of interest, mystery, intrigue and hurt feelings. If we do want to figure out what the COS policy, please remember to be respectful of other customers aliments - regardless of the cause - and address the issue with discernment.
My thoughts are that as a customer you buy a 'cube' of space on a plane. If for whatever reasons you are unable to fit into your cube of space, you run the risk of imposing upon a fellow passengers cube. I think SWA's policy makes sense - if the plane is not full, then the COS just sits next to an open seat and imposes upon no one else’s cube. However, should the plane be full, the COS needs to respect his or her fellow passengers and enquire about purchasing a second seat at a discount.