f actions. Based on lessons learned from this initial effort, the approach was extended to constructing a crew model with a simulated PF and Pilot Not Flying (PNF). These crew members were simulated by separate ACT-R models based on a cognitive task analysis of the duties for each person. The simulated task scenario was the time period just before and after Top of Descent (TOD) in the descent phase of flight. The PNF tasks included verification and programming of the Flight Management System (FMS) computer as well as gathering appropriate information for completion of the flight. The PF monitors and flies the aircraft except for required briefings and responses. Required aspects of crew interaction such as crew communication (e.g. briefings, acknowledgments) were implemented by a communication link between the PF and PNF simulations using a multi-model extension of ACT-R. Simulated communications involved goals, specific actions, or situational facts and features. The linked PF and