United Hidden City Ticketing to a Train Station to Make Newark Flights Cheaper

United allows you to book trips to and from ZFV, Philadelphia's 30th St. train station. Such fares include flights to or from Newark and trains from there to Philadelphia.

Because in the short term an airline's ticket prices have more to do with competition from other airlines than anything else, United often sells tickets to ZFV for cheaper than flights to Newark, even when the trip to ZFV is the same flights to Newark plus a train ride.