I was under the impression that Amtrak from Newark Airport to 30th St Station in Philadelphia was available as an airline code share (and that train segment is fast enough that there's no good reason to get on a plane for Newark<->Philadelphia, even if you are connecting to another flight out of Newark), but I haven't figured out how to find such a code share with Google's flight search tools.
(The governor of IL and the Chicago mayor also asked Amtrak to study how to extend some of the Amtrak routes to O'Hare, presumably to replace some ``commuter'' flights, and they wanted the study done by the end of this summer, but I haven't seen any evidence of the study being done yet.)
(The governor of IL and the Chicago mayor also asked Amtrak to study how to extend some of the Amtrak routes to O'Hare, presumably to replace some ``commuter'' flights, and they wanted the study done by the end of this summer, but I haven't seen any evidence of the study being done yet.)