Systems engineering and program management (SE/PM) constitute a large portion of the acquisition cost of military aircraft and guided weapons systems. The goal of this study was the development of a set of cost-estimating relationships that can be used to estimate the SE/PM cost element for development and production of aircraft and weapons programs. The authors investigate trends in SE/PM costs over time to generate methods that cost analysts can use early in the life cycle of a program when little cost information is available.