We present a modular method for schedulability analysis of real time distributed systems. We extend the actor model, as the asynchronous model for concurrent objects, with real time using timed automata, and show how actors can be analyzed individually to make sure that no task misses its deadline. We introduce drivers to specify how the environment may interact with an actor. Using these drivers we can test schedulability, for a given scheduler, by doing a reachability check with the UPPAAL model checker. Our method makes it possible to put a finite bound on the process queue and still obtain schedulability results that are correct for any queue length.