AA initially discontinued lots of non-stops from JFK to most European destinations (except to LHR), forcing pax to connect via PHL; now that they are killing the PHL market is not too surprising, this is the "new" AA.
I quit AA for DL months ago and have had no regrets. By the time AA realizes they've lost a big chunk of the northeast market it will be too late to woo that market back.
The typical NE market to Europe could care less if they connect at JFK, or EWR, or PHL, other than the NYC market. Further, AA's PHL European portfolio has changed little,except for tweaking, since before the JFK downsizing. OTOH, AA/JFK has Barcelona, Madrid, Milan, Paris, London and Rome. It's called NYC greed - take away a NYC dime out of their billions, and they feel picked on.
