"For purpose of clarification, the airtrain stops at NJ Penn Station FIRST"

WOW. Totally false information -- I would ignore that entire post. The air train does NOT even go to NJ Penn Station (I think this person meant Newark Penn Station, I know of no NJ Penn Station). But in any case if you don't get off the air train at the Liberty airport stop, you will just return to the airport itself and could keep circling for hours. You must get off the air train at the Liberty station and take NJ transit directly from there to New York Penn Station.