Has anyone booked a ticket on Continental and put in "ZFV" instead of EWR to look for lower (often significantly) fares???
ZFV is Continental's "airport" code for Philadelphia train station and they for the most part match all of the fares from Philadelphia airport, which are often lower than from EWR. The flights are actually from EWR but come with a free train ticket (usually they are essentally PAYING you to take the ticket) from Philadelphia city to EWR. These train tickets are very expensive; even though the ride from Philadelphia to EWR is only an hour, Amtrak charges over $100 round-trip (standard non-Acela service)!
Continental has no way of know whether you took the train ride, so you can either throw away the train ticket and just take the lower fare if you live near or north or east of the airport, or take the train from Philadelphia, Trenton, or Metropark.
Often they are PAYING you to take the train ticket.