95b323b7_of_Size__Policies___Yahoo_News__Stated_policy
[Airline] Alaska [Costs] In advance, the second seat is the same fare as the first. At the airport, the lowest available fare at the time will be offered. Yes. As long as there were empty seats on each leg, you may request a refund after your trip. [Stated policy] 
Passengers must fit within the 17 inches between armrests or purchase a seat in advance. Those who do not cannot be guaranteed boarding.
Airline "Customer of Size" Policies - Yahoo News
Stated policy