I'm flying SFO-PEK round trip towards the end of this month, UA 889 and 888. Currently I have an economy ticket at less than a W fare. Both flights currently have NC 0 (which I think is the right code to check), so I couldn't apply a SWU if I could obtain one, but have 9 Z business seats for sale and about 20 open business seats on the seat map. I have aisle seats in Economy Minus right now. The Economy Plus seat map has only open middles, both ways, so that is not a better option. I'm considering calling and up-faring my ticket to the W fare, then trying to find SWUs. (A college friend posted on Facebook that he had one available, for instance.) But I don't have experience with availability, and don't want to waste money. Given the amount of open business class seats, will upgrade availability open? If so, when? Also, can I call and change my fare in just one direction?