flying sun country from Minneapolis to Vegas this summer. 3 hour flight and 1st class is a 169 dollar upgrade (each way) up to an hour before take off. (Boeing 737-800) My question is can you do anything like "the 20 dollar trick here"? do the gate agents have any wiggle room? If a half hour before the flight takes off and they have empty seats up in first class are they more inclined to upgrade people?