The best airport to use for travel to Bethlehem is the Newark Airport (EWR). This airport is 73 miles away from campus, and has a dedicated bus line that will drop you off a very short distance from the hotel and campus.
If you prefer to rent a car, please note that you will have to pay a toll.
Philadelphia airport (PHL) is 77 miles from Bethlehem, and will require a car rental.
JFK airport is 104 miles, which is drivable though it does require crossing New York City. The bus also goes from JFK to Bethlehem, though the bus schedule from JFK is only twice a day.
Allentown airport (ABE) is 14 miles from Bethlehem. This airport is small and only has about 10 flights a day.