I flew back LHR-SFO this morning and observed lots of operational upgrading--and, indeed, benefited from the highly unusual (for me) double upgrade from Y to F. I was on a B-fare Y-class ticket and it cleared the upgrade waitlist some time over the weekend. When I checked in, the agent said "you've been upgraded to First Class courtesy of United" -- and sure enough it was an F boarding pass showing my booking class as NC (my upgraded business class). Wow. Looking at the manifest in F I saw that an agent had marked six of us as "OPUG" and that at least a third of C was similarly marked -- coach must have been heavily booked with few revenue C or F seats.

It was a good flight, too...