Once was sat next to a very large person to the point of not being able to cope with the situation for a 4 hour flight.
I asked to be moved pre departure but was told flight was full.
Said I couldn't do the flight like this.
I removed myself from aircraft, was denied a new booking or a refund.
So I paid for that fat funks gut to get a comfortable ride.
Moral screw them and make them pay.