Originally Posted by
Zeffer
I'm delighted and frustrated to hear that same day flight changes retain the upgrade priority of the original booking. I'm currently sitting at LaGuardia four hours before my flight to O'Hare, and every flight is so oversold that none of my standbys are clearing. This morning I had the option to make a same day change to the flight that just departed, but I declined to do so as I didn't want to nix my upgrade chances. Fool!

The upgrade request stamp is part of the PNR, so whether you do CFC or change your routing altogether, you will retain the original upgrade stamp as long as all of it is done in the same PNR. If a new PNR is created, then you got a new upgrade stamp as of the moment the upgrade is requested/renewed/refreshed