With AA/US offering nonstop flights from PHL for $662 (or $622 for 2) Delta is now offering flights from PHL via JFK for $677. Well that's actually great news for New Yorkers. Delta is offering flights from JFK for $875. If you search a multi-city departing from JFK and returning to PHL you will find flights starting at $779! (just make sure the stop is in JFK) Sample dates that I found at this price: 1/19-2/2. Plenty dates available. Bookable on Expedia.com and Orbitz.com (or Directly with Delta)
Helpful tip: To find dates that apply, Search flexible dates on Kayak etc. from JFK roundtrip and then search from PHL roundtrip, and the dates that are cheap from both airports should combine for this sale.
(p.s. For those who aren't familiar with how this works, "noone is obligating you to continue to PHL")
