Not sure I'd call PHL a threat to JFK. It stood on its own quite well before the merger and now provides more flexibility for routing passengers heading across the Atlantic. AA can focus on more O&D to high yield markets from JFK, as well as lean on OW partners there. Due to the slot constraints, they are somewhat limited in how to use them. It seems they will optimize those slots for strong revenue/high yielding routes like LHR and LAX. PHL, on the other hand, has more flexibility to add routes that will hopefully have strong O&D *AND* funnel connecting traffic more efficiently. The PHL international terminal A-West is as nice as JFK T8 in many regards....not as big, but still has the 'international' gateway feel...
bolding mine. And this gap will shrink considerably when PHL gets a FL (although that could be 1+ year away it seems)