Originally Posted by
iapetus
If so, when does the SDC window open? My first leg is LAX-IAH at 11:40am on March 22nd. Does that SDC window open at 11:40am on March 21st? I see no restrictions on waived SDC charges for international flights; that is the case, yes?
Yes, you can SDC international flights, provided all downline flights are UA-operated. So, it really only works if MUC is your final destination, and you won't be able to change to EWR-FRA. And, the SDC window will open as soon as you are within 24 hours of both your current and target flight.
Note that you may have a hard time transferring a waitlisted upgrade instrument. Some agents will do it; some will say "no new waitlist requests within 24 hours of departure." If the flight you want has PZ inventory, though, you're golden.