Originally Posted by flyerwma

Another option is to stay on the same PNR, check-in online (if you want to coordinate bag check early), and then re-check-in at kiosk at the airport.

When I have done this (typically in cases when the SkyPriority line was very long and I wanted to try and use the regular bag drop), the kiosk would prompt me to ask if I wanted to be on the upgrade list, without splitting me off the PNR.

(Some will ask why this only works on kiosk and why it can't happen for OLCI. Others will find banging their head against the wall more satisfying).

Of course, this only works for battlefield upgrades, and not UGs at the window.