Originally Posted by
zrh2yvr
If they have officially announced a delay, the system will be updated to allow/expect passengers to check in assuming the new departure time. This is one of the reasons that airlines often wait until the last minute to post a delay because once you delay - it's tough to go back and reverse it (but not impossible).
While that might be the official answer, my experience is that once a flight goes into delay mode you simply cannot believe
anything anyone at AC tells you. I have never trusted them to advance the bag drop time, nor would I recommend it.
I have also seen them move up a departure time after posting a delay. They sometimes decide that they're ready, round up whomever is at the gate, load and go, leaving behind a few who wandered off believing the posted time, although that was admittedly quite a few years ago.