Originally Posted by
mfirst
why would you want or need to undo a check-in?
In my case I was assigned BG2 instead of BG1, so I undid and redid checkin to try to fix. (Turned out I was part of an unannounced test of a new boarding order.)
IIRC, you can also split PNR for CPU on a re-check if you say no the first time.