Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
The OP's problem on this particular route should evaporate in a few months, when all US-coded flights become AA-coded flights. But for now, the solution, as indicated, is to book two one-way redemptions, rather than a single roundtrip redemption.