Delta Shuttle won't go to RJs...they do that and they'll lose everyone over to the US Airways Shuttle. The yields are huge on this route - a lot of full fare tickets on here so that a 50% full shuttle is still most likely generating profit, even at a reasonably high CASM due to the use of MD-80s and that on the shorter flights the ratio of fuel burn is a bit higher since the climb portion is a proportionally higher percentage of the flight.