Originally Posted by
Tafflyer
Usually though, especially starting in Europe, AA will have better fares these days than BA, even if the flight is BA metal.
Well usually AA have exactly the same fares as BA - that's the point of the JV.
They do sometimes offer different fares, but my guess in OP's case - without having checked the fares - is there's simply a lower bucket available in BA inventory than AA inventory. Trying a different POS might even it out but I don't know what POS is required for the voucher.