Taxiing an airplane at a major airport requires the pilot to interact the world outside the cockpit, the instrumentations within the cockpit, and the co-pilot. As many actions require time to pass before their outcome can be evaluated, the pilot must have an approximate sense of how much delay should occur before the outcome of an action can be evaluated. Finally, taxiing is a paradigmatic example of multitasking. These three ingredients (a) a high level of interaction with dynamic task environments, (b) a sense of time, and (c) multitasking, present challenges for theories of cognition and the building of process models of taxiing. We describe a model, SimPilot, its initial validation, and its implications for cognitive theory.