I checked the original email from AA.
The link to the contract of carriage is:
https://www.aa.com/pubcontent/en_US/customerService/customerCommitment/conditionsOfCarriage.jsp
Link from my email is broken. Googling for the contract of carriage gives me this:
https://www.aa.com/intl/es/footer_en/conditionsOfCarriage.jsp
It says a 30 minute cutoff time.