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Abstract—Large commercial aircraft maintenance facilities are characterized by the simultaneous layovers of multiple aircraft undergoing a wide variety of maintenance checks and modifications. The organizational layout of a maintenance hangar normally includes a tool dispensing store, or tool crib, from which aircraft technicians sign out special tools to carry out specific tasks. Efficient operation of the tool crib ensures that the non-value-adding time spent by technical personnel queuing to be served, and while being served, is kept as low as possible, therefore increasing productivity and minimizing the risk of delay. In this work, a detailed study of the operation of a tool crib in an aircraft maintenance facility is carried out. A detailed and versatile simulation of the operations is developed, based on real data collected at the facility with the aid of a new software tool to facilitate event synchronization. The empirical analysis is augmented by and compared to a theoretical study of the queuing behavior of the environment. The simulation is then used to investigate quantitatively the effects on the overall waiting time of varying the stock levels of critical tools, of reorganizing the tool storage locations, and of changing the number of human servers. In the context of the case study, it is found that relatively minor changes in tool crib organization can result in substantial savings both in the overall waiting time and in unsatisfied tool requests.