Within the last month I watched more than a half dozen people get op'd up from coach to first on the ORD-EZE route, while I was sitting in business. I am only a 1K so maybe there were GS in coach, but if there were why didn't they upgrade to business earlier? I checked the manifest on the first flight and there were no GS in business and as a 1K I was in the minority. Either they were all op-up'd prior to boarding and weren't part of the shuffle I saw or there weren't any in business.

I know you can't tell a GS by their appearance, but I don't think all the double op ups were GS. How does United pick who to op-up and why would they pass over the 1Ks in business (even if they used SWUs) and give double op-ups when the flight is ahead of schedule and there is no rush?