I have again experienced the pain and suffering of a domestic flight, nearly coast to coast, sitting next to someone who is really too large to fly on planes. I don’t want to be rude, but if you are so big as to not be able to sit in a single seat, lower the arm, or use a single seat belt, you need to buy a second ticket.
Forcing thin, tall people to sit next to you and be mashed into the aisle is no way to be friendly with others. And I could certainly do without all the sweating and snoring.