DFW-PNS is about 2 hours.
Honestly though, this is how the RJ's should be used. To seek out new routes and raid other airlines territory. PNS is traditionally DL territory, but I think AMR knows that DL's DFW hub is dying. So they are taking advantage of that fact and raiding the market.
If AMR brought in MD80's into this market to start, they'd hemorrhage cash. In time, if the market responds to AMR's service, they can then begin upgrading the route. PNS does support mainline from other carriers (Airtran, Delta, USAirways) so in time it may be able to support AMR mainline. But you have to give the market time to develop. AMR has little name recognition in this part of the Deep South.