Originally Posted by christep
Good point (although did you really need to quote my entire post to make it?). The Platinum Challenge is probably the way to go given the importance of lounge access - I'd forgotten about that. Just remember that if, for any reason you need to go through the US then the transatlantic piece will have to be on AA, not BA.
However, even if that transatlantic piece is on BA, I believe the OP will still have lounge access as a OW Sapphire on a OW flight. There just won't be any elite qualifying miles.