I live in a non-hub city and am planning travel to a hub city. There are non-stop flights between the two, but I've found a cheaper fare using my desired destination as a connection point. My plan is to buy the cheaper fare and get off at the connection point, leaving the second segment unused. Obviously, in order for this to work, I don't plan on checking any bags, and my return trip won't even be on the same airline (although I suspect I could get away with it if I booked the return on a separate PNR).

The wrinkle is that there's also a non-stop flight between my origin and my "fake" destination. For example, I could take a flight that leaves my origin airport 40 minutes later and arrive at my "destination" 2 hours earlier. Of course, this route doesn't do me any good, since it doesn't go where I want to go. I'm concerned that if I execute my plan, when I show up to check-in (or perhaps even before I check-in) the airline will reaccommodate me on to the direct flight. Are they likely to do this, and if so, do I have any chance of getting them not to change my itinerary?

FWIW, the likely carrier for this endeavor is AirTran (Delta might also work).