Another thing you need to be aware of is the airplane. I think American is still using the 767-300 on the PHL-PRG route. That airplane type is relatively old and definitely not the most reliable. They're known for major delays. I just got back from Zurich on one and was on time both ways - you can be lucky, but my last trip on a 763 before that was OGG-DFW, and we took a three day delay due to a mechanical problem (you won't have that kind of a delay ex-PHL; I'm sure they have alternatives and 767 parts either there or at JFK) but it is a concern.