WN has 2 different HOU-JAN-BWI flights that have 20 minute scheduled turns in JAN. I remember reading a few years ago when Southwest was experimenting with the dual jetways that, prior to the experiment, BUR indeed had the fastest turn times because deplaning and boarding were done with airstairs from both ends of the plane.

Although they can sometimes turn a plane in less than 20 minutes, I think 20 minutes is the shortest scheduled turn time.

Mike