There is a Free, frequent inter-terminal Shuttle Bus that runs between Terminal AEast - Gate A1 (Closest to International Arrivals/Customs/Immigration), Terminal C - Gate C-16 and Terminal F - Gate F14 (Closest to your Southwest flight in Terminal E). The Bus runs inside the secure area, so you never actually leave the airport. Check with American for directions after your arrival. Walking (without the Bus) should take no more than 20 minutes, without luggage.