Short schedules and changing requirements are common problems encountered when software is being developed for training systems. This paper explores techniques used by Technology Service Corporation (TSC) to overcome or avert such problems while developing the B-52 OAS Part Task Trainer for the Training Services Division, Keesler Air Force Base. Techniques for dealing with limited resources (time and budget) include carefully exploring, and assigning priorities to, system capabilities to determine the more important requirements; and employing a top-down approach. Planning for changing requirements calls for identifying capabilities that may change; constructing a well-documented software design with application-oriented modularity; and scheduling a design freeze, with late requirement changes incorporated after completion. The paper presents step-by-step descriptions of each technique and provides examples relating directly to the part task trainer.