I had an odd experience last night. I'm traveling LAX-SFO-HND-KIX today. Last night night, at the 24-hour mark, I tried to check-in for my LAX-SFO leg. However, it went through all the international check-in nonsense and then didn't let me check in.
I didn't expect it to let me check-in for the Japan Airlines international legs, but I thought it would at least allow the domestic.
Oh well, no worries. This morning, I checked in online with JAL for the SFO-HND leg and went back to the AA site and, lo and behold, I was already checked in!
Go figure...