This technical report documents the development and initial empirical testing of a practical method for estimating the capacity of Air Force operational units to conduct on-the-job training (OJT). The method is based on a conceptual model of OJT capacity that describes the complex interrelationships among the level and quality of mission performance achieved, and the amount and quality of training provided, by an operational unit. The unit's capacity to conduct OJT is then determined as the maximum amount of training sustainable by the unit without compromising established training quality and mission performance standards. The model has been empirically tested by estimating its basic structural equations, to the extent possible, using existing data for six operational units. Despite substantial limitations in data availability, the empirical analyses reveal, for all units studied, a persistent and strong inverse relationship between the training load of a unit and the mission performance quality of the unit. These favorable results indicate that further development of the OJT capacity estimation methodology can reasonably be expected to significantly enhance Air Force training management capabilities. (Author)