I thought I understood international mileage upgrades pretty well, though to be honest, I've always picked flights based on NC availability and have never had to be waitlisted. But an otherwise very knowledgeable phone agent made ma doubt what I thought I knew. She said that being waitlisted for NC is essentially hopeless because they "never" open up additional NC inventory until the day of the flight, and even then they usually sell enough upgrades not to have to take anyone off the waitlist. That doesn't sound right to me.

(I asked because I just saw the NC inventory for a GVA-IAD flight go from 3 to 1 and I'm trying to decide whether to purchase two separate itineraries so I can immediately upgrade my non-status wife and place my 2P self on the waitlist. This would seem to increase the chances of both of us getting the upgrade on this flight, but would decrease the odds of ending up together in C for the outbound ORD-CDG, which is NC0 and thus would require us to be waitlisted separately.)