How should enlisted initial training be divided between centralized initial skills training (IST) and decentralized on-the-job training (OJT)? This document provides recommendations to address this question based on a cost-benefit analysis of seven Air Force specialties. The underlying methodology includes a mechanism for developing specialty learning and productivity curves that are used to capture the full human capital development (HCD) cost (IST and OJT). All too often, only IST costs are considered when pricing training. When this is done, the overall cost to train an airman is seriously underestimated. When the full costs are considered, decisions related to the length of IST are better informed. The Air Force typically trains 30,000 to 40,000 new airmen in some 300 specialties each year. We estimate IST costs at $700 million per year, with OJT costs reaching perhaps $1.4 billion each year. In developing new airmen to required levels of productivity, IST and OJT can, to some degree, substitute for each other. An appropriately designed cost-benefit analysis is necessary to find the best balance between them. Productivity is difficult to measure. We equate a productive airman with one who possesses the skills to be fully mission capable. But then, in what ways must an airman in a particular specialty be skilled in order to be fully mission capable? How should a training program prepare airmen to obtain these skills and this experience? At what skill level do airmen currently graduate from IST? How does productivity increase with time in OJT?