Correct, Tupolev154B2...They fly on off peak routes with low capacity. Probably the longest route with a DC-9-10 would be DTW-DFW, about 2-2.5 hours. They are also used on flights like MSP-RST (Rochester, MN), and MEM-STL. They are slowly being replaced with Mesaba's RJ-85s, with the CRJs going primarily towards high-cap routes formerly operated with SF340s (Think MEM-MOB and MEM-TUL).
Create your own luck.