AA has basically retreated quite a few fights from JFK>PHL. This would indicate they see the need for connections from smaller cities that still don't have Ultra low cost European carriers. NYC-Europe fares are just crashing so this is a really smart move for them. I think they can see summer 2018 will be even worse, best to get these moved now. JFK has too many of these lower cost airlines, no reason to bleed money there. Best to focus on PHL and preserve their fortress hub.