I guess I simply don't understand the Mileage Plus Program. I've accumulated about 100,000 miles. Trying to use them for upgrades (such as SMF-DEN but others as well) booked at the time of booking. No matter what date I put in - even almost a year out- it is showing these are standby only. Does UA EVER confirm mileage upgrades at the time of booking? I'm sure not finding any. And if I just want to use miles to book the flight in F, it's showing no flights available for non-stop flights almost a year out. Am I doing something wrong in my search or are my miles essentially useless for first class travel on UA? And even when I can book F class seats using an upgrade and on standby, UA charges some sort of "service fee" of $75 per person-- what's this all about???