If you are from out of the region and need to fly to AC on AA, I still would think the door to door time is shorter by just getting off in Philly and renting a car. it's almost exactly 1 hour from PHL airport to downtown AC by car. Maybe a little longer if you hit rush hour in the PHL area and bridge. By the time your half way there, the PHL-ACY bus will be boarding and by the time you get into downtown AC, the AC bus will be 40 minutes behind you.