There is a shuttle between the two concourses. I tend to go through security on the US Air side and shuttle to flights at the AA gates because the US Air security has TSA Pre-check. Since the shuttle is on the airside tarmac you have to be ready to occasionally sit for a while if planes happen to be departing from the gates the bus goes past. I have been on the bus for >20 minutes for a very short ride. AC on the AA side is reasonable and has very nice staff. I would not describe it as elegant, however.