Agreed. Looks at the AA route map first. There is availability to most destinations in Y. Do a dummy booking on ba.com, it will say "BA does not fly from ATL-beachland" do you want to search for "partners airlines". And it will show all AA availability and give you the price in Aviowotsits and $$ fees/taxes.

Not much different to walking into CVS and buying a tube of toothpaste really, once you've decided what brand you want.