I ran into this issue over the weekend, overall terrible service from AS.
I was mid-trip on June 20, scheduled to fly from BOS-SEA-DEN on June 23rd.
Got an email that AS cancelled the last SEA-DEN flight of the day going forward.
I'm used to advance schedule changes, but to cancel a flight 3 days before is a bit disruptive.
Called AS, and the best they could do was put me on a SEA-DEN flight a week later!
Not sure why they cancelled if there was so much demand, but AS basically told me to pound sand. No alternate routing possible, no other airlines offered
Since this was within a few days of flying, other options were nearly 4x the price I paid.
Ended up with a forced overnight in SEA at my expense, with a nail biting standby experience this morning.