Greets,

I am upgrading an economy ticket MEL-HKG-LHR-HKG-SYD with MPC points. I booked the upgrade first, and then got the economy ticket to match it. I've faxed it to MPC and have received confirmation of the upgrade.

Apparently they don't reticket the itinerary, but will instead post me a voucher that will be processed at check-in.

That means that I now have two reservations with that show up on cx.com. One is the economy reservation, the other is the business class reservation, both on exactly the same flights. Doesn't this mean that once I get upgraded at the airport, my economy seat will go unused?

Is this really how it works? I guess it's possible, since they probably overbook flights and the free seat will get used by somebody else.

Sometimes I get confusing/conflicting info from different MPC agents and I want to be sure.

Thanks in advance.

That is exactly how MPC processes the upgrade. You can have two separate PNRs but you can cancel the Y booking, if you like. Since the two PNRs are linked, I don't think it would have a major problem for seat controllers.