Originally Posted by
rustykettel
pbd456 is correct by the written rules, but in practice you'll earn based on the operating carrier's chart. In this case BA.
Save your boarding passes, in case you need to send them in for retro credit!
+1 This is the only way to get it done, but caveat emptor I have seen BA tickets that say "Sold as AA####" or have other indicators that the ticket isn't originally BA. Good luck ^