I use SmartPark at PHL. It is located in Essington on the South side of the airport. Their service is pretty good and their rates aren't horrible. Definitely get a coupon if you are going to use them I think they are for $5.95/day.(without a coupon it is either $13 or $14/day. -- stop by a travel agent in the PHL area -- they usually have them. 16 days is a long time and even with a coupon for $5.95/day will cost a bit. You might be better staying at an airport hotel the night before your trip and leaving your car there (some offer you free parking for your trip if you stay overnight -- I don't know which hotels offer that though).