The rule is that if you have the award issued with a downgrade, and later find available inventory, you must go back to the issuing airline (presumably AA in your example) and reissue the ticket for business instead of coach. Sometimes CX will "op-up" you, BA usually will not, and IB and LA definitely will not under any circumstances. The problem is that the flying airline is paid based on what the flight coupon says -- not what your award cost you. So it is money out of the pocket of BA/CX/IB to subsidize what to them is an AA customer; not much incentive to do you any favours unless of course you also happen to be BA Gold or CX Diamond, etc. In practical terms getting the re-issue done is next to impossible. You must assume that once you accept a downgrade, you are locked in.