Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

To redeem BA Avios for flights on AA, you must first log in to your BAEC account at ba.com, and then indicate in the booking engine that you want to pay with Avios.

But before bothering to do that, I would go to aa.com, and check award-seat availability there. (No log-in required at aa.com.) If you find nonstop Coach award flights offered at the "MileSAAver" level, then you should be able to find those same flights at ba.com.

However, if you only find connecting-flight MileSAAver award itineraries offered on aa.com, BA will charge you more than 12,500 Avios, since BA now charges for each flight flown.