95b323b7_of_Size__Policies___Yahoo_News__Stated_policy
[Airline] American [Costs] Two adjacent seats will be offered at the same rate in advance; if you have not handled this when you arrive at the airport, see an agent before proceeding to the gate if empty seats are available, you may be able to snag one for free. None specified. [Stated policy] 
Customers who are unable to fit into a single seat, unable to properly buckle their seatbelt with an extender or unable to lower both armrests without encroaching must address their seating needs when booking the original reservation.
Airline "Customer of Size" Policies - Yahoo News
Stated policy