Originally Posted by
enviroian
I've never seen it anything other than T-4
My understanding is once the list appears on the app, the list is under airport control. I based my previous answer on the following from aa.com:
Step 2
If your upgrade is confirmed, we'll send an email to the address in your AAdvantage profile to let you know you've been upgraded.
If you're not upgraded right away, we'll keep checking for upgrade availability – up to 3.5 hours before your flight.