I had a schedule change of about 10 minutes once and I saw an opportunity to jump on a later flight, which I wanted originally, but it priced out higher. It cut my connection to London by about 2.5 hours. It wasn't a problem. In fact I also received an apology for the inconvinience (it wasn't necessary
), but I agree with
aaupgrade, you can't change your itn to a different day or jump over the same day available flights just because of schedule change. Let's say your 8am was changed to 7:45 am, but there are 9, 10, 11 am flights available. You will have a hard time convincing the agent to put you on the 11 am flight, but the 9 should be no problem, as long as there is availibility.