My mom had a schedule change for a flight a couple of weeks away. Domestic paid F, the connecting flight went away, the system rebooked her on the next one, turning a 70 minute connection into a 4 hour plus stopover.

We decided what alternative we preferred - leaving an hour earlier and thru a different connecting city, and messaged twitted with the change request. A half hour later, it was all confirmed as requested. So kudos to AA for making that so easy.