Originally Posted by MikeMpls
My recollection is that the paid upgrades at checkin are only for higher fare classes -- H/M/B/Y. How much will depend on distance and fare class (cheapest to upgrade Y).
I would expect upgrades for DTW-SFO to be very competitive for silvers and even golds; sometimes even plats sit in the back.
It is even EXTREMELY competitve for Plats. Always full of Plats and many times Plats don't get it.