Originally Posted by justcallmedoc
Now, I don't believe the FA at check-in has anything to do with your upgrade. Every time it happened to me, I only knew at boarding, as it was probably decided by the ground staff seniors whom you don't see but who check the filling of each class (and then decide to upgrade you based on your FFP level, the price you paid and also possibly your country of residence - my best bet is that non-France based PAX get better treatment).
On the ~10 op-upgrades I have got (from Eco to Bus) two have been made at check-in: one in CDG, one in MIA.
In both cases summer flights, full in Eco, and I was FP Red. And it was already decided, as you say the check-in staff was only applying something already decided.
In all other cases upgrades have been made at the gate, once known the exact number of passengers checked-in.
Will fly CDG-CCS in Aug 7th, the flight is already full in Eco, wide open in First and Business, interesting to see what happen now we have FB: as a Plat I would be quite disappointed no to be upgraded: in all similar occurrences (same flight, summer months, full in eco), I have been upgraded.