AA awards are dynamically priced for members of AA's frequent-flyer program, essentially meaning that AAdvantage members get last-seat award availability on AA flights, but sometimes at very high redemption rates. However, AA makes award seats available to partners only when those seats are offered for relatively low prices to AAdvantage members. Therefore, you might find it challenging to find Avios redemptions on some AA flights -- especially in premium cabins. And AA only makes its flights available for sale (with cash or miles) at T-331 days, not T-355 days like BA. I'm not sure how you are seeing availability for mid-May, 2026, on AA flights, as the AA awards booking engine is only permitting searches through April 24. Did you perhaps mean mid-March instead?

AA also uses married/divorced-segment availability, whereby two flights might only be available to partners if booked separately, and not as a single redemption (or vice versa). The other possible issue you will face is that ba.com sometimes has problems displaying connecting-flight itineraries for redemptions on AA metal, even if a call center might be able to book such itineraries.