It's as
sukn says, unless you are upgraded at the gate or the like. Your upgrade must have come through by the time you check your bags in, even if it's at the ticket counter somehow, as far as I understand the issue.
Originally Posted by aa.com
Attention First and Business Class Customers
We are pleased to offer customers in First and Business Class the ability to check three bags at no charge when traveling on American or connecting with British Airways or Iberia. (23 kg / 50 lb from / to Ecuador)
link