I talked with AA about flight number changes that I received by SMS some days ago and they also talked about web check in, if I wanted to do that. I asked a few questions about that also & one of the things they said was that If I checked in months ahead and for some reason couldn't fly on that day and wanted to change it, I couldn't. It was locked in and cannot be changed or deferred. May not be a good idea to check in too early, but much closer to the day.