I've booked a round trip to the US, flying into New York with BA but returning home from Cincinatti with AA for the major part of the flight. I'm thinking about getting extra leg room which is fine for the outward leg with BA, but I don't have any option for the return leg to either book that, or even paying to select your seat. I tried calling BA to ask earlier but there was a half hour wait on the phone, and it was an 0844 number so didn't fancy that much!

Does anyone know what happens for selecting your seats or booking that through AA?

Thanks