I mostly fly with, and credit my miles to, US Airways, but I end up on more United flights than I'd care to in order to fill some gaps (riding a turboprop direct MCI-DEN is better than flying on A319s and connecting in Phoenix). For some time now the joke about United has been that the only mainline flights left are the international routes and the hub-to-hub connections.

And then the other day I saw someone point out that there are now hub-to-hubs on United Express regional jets.