Once you get outside of the two big cargo carriers, there is just as much volitility, if not more, on the box-hauling side. AMCI carriers come and go much more often than pax haulers. You don't hear about them because they're usually small ops with just a few aircraft.
Don't know what to tell you other than that. Seems that the regionals are just the first step inside the door. After that it seems that people will go in a ton of different directions. Some to majors, some to the big cargo guys, some to the smaller ones to get to the bigger ones, some to fractionals and so on.