The Navy's Tactical Aircrew Combat Training System (TACTS) provides the instrumentation necessary to record in-flight performance of aircrews during air-to-air combat training. Data recorded on TACTS has been an important source of information for the development of objective flight performance criteria. This paper discusses research related to the development and application of in-flight measures of air combat performance. Procedures for systematic development of aircrew performance measures are identified and discussed. A generic methodology is proposed which will eventually lead to a prescriptive model for performance measurement system development. Some of the many applications of objective flight performance criteria include training progress evaluation, training methodology and effectiveness studies, and learning acquisition and transfer studies.