Yes. The train that runs from the station to the airport is free.
It is not necessarily 'free' since an additional fee becomes inccured in your ticket price, which is known as the 'Airport Surcharge' fee. It is about $5 or so. For example, a one-way train ride from NYP to this station (using NJ Transit) should be around $11-$13. However, the additional fee makes it at least $16. The same is also true for Amtrak trains, and every other train that stops here. Consider this 'fee' as the price you would pay to use the AirTrain (similar to the situation at JFK).
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