United Airlines Policy for Portly Passengers

Seat Sizes
Seats in the economy section of a United Airplane measure between 17 inches to 18.3 inches depending on the location of the seat (aisle, middle, window).
Seat Belts
Seat belts are measured at 31 inches long while their extenders add approximately 25 inches to the belt, passengers must request a seat belt extender prior to their flight.
Policy for Overweight Passengers
United’s seating policy for overweight passengers is noted as stating “A customer flying in the economy cabin who is not able to safely and comfortably fit in a single seat is required to purchase an additional seat for each leg of their itinerary. The second seat may be purchased for the same fare as the original seat, provided it is purchased at the same time. A customer who does not purchase an extra seat in advance may be required to do so on the day of departure for the fare level available on the day of departure.” – United Airlines Special Needs Accommodations Website
With their policy written that an extender must be requested prior to boarding this can be daunting and embarrassing for new travelers.