I've rented cars in a number of airports across the US but only at SEA/TAC do I consistently get a Toyota Corolla even though my company contract is for a mid-size. And there are plenty of mid-size cars around the lot. I am President Circle and usually get upgraded to a full size (Tarus, Camary, Five Hundred) and IAH is usually very nice to me giving me a SUV. Why do certain airports downgrade?