Originally Posted by
corporate-wage-slave
That is exactly what used to happen, you can actually watch the exercise from inside the airport and on the usual aircraft tracker sites (since the AA lounge don't have views in that direction), see the thread below. The lovely AA lounge staff there would regularly call their chums around the airport to track what was going on since it was an interesting daily ritual for them. It's all ultra hypothetical at the moment, but I think the AA lounge will contine to be the BA lounge, without double security. The only current service are the BA codeshares, and they of course do have AA lounge access.
New BA Routes 2018: Nashville, Tennessee (BNA)
Pre-COVID, the BA gate ( gate B11 ), and the C concourse were connected airside. Now there is a construction going on at BNA which required the BA concourse and the AA concourse to be split with no airside connection. Pre-COVID the BA flight never operated from the C or D concourses which is currently the only concourses linked to AA Admirals Club.
By the way, for the moment, yes, only BA codeshares are operating from BNA.