United Airlines to Charge Overweight Passengers for Two Seats

[Alex]

Nope, and also if they have to change planes and reseat everybody.

Or if you're flying with your child and the plane isn't full but there aren't three consecutive seats so that you can still be seated with your child.

But the other airlines have been dealing with this for a while now so I'm guessing there's a fair amount of discretion available to the gate and flight crews.