We recently flew AirTran out of Philly to Chicago, got to the airport two hours ahead of time, waited 20 minutes for the Economy Parking bus (this was unusual for us), and had about 35 minutes to spare. We used the e-ticket machine, and that saved some time; although we still had to get in a line to check the luggage. The lines were short - it was waiting for the parking bus that took time. My son flies AirTran to Chicago a lot and gives himself less than an hour (he usually just has a carryon), but I wouldn't suggest that. It also depends on the departure time. Mornings seem to be more crowded, especially US Airways. I'd probably go with the two hours just to play it safe. I don't know how you're getting to the airport, but the Blue Route and 95 always seem to have delays. Hope this helps. Joanne