A FlyerTalk Posting Legend
Join Date: Sep 2012
Location: SFO
Programs: AC SE MM, BA Gold, SQ Silver, Bonvoy Tit LTG, Hyatt Glob, HH Diamond
Posts: 44,346
If there is I-space on the flight, you can do the change through Aeroplan and get it confirmed in J.
If there is no I-space, the SDC is going to keep you in X.