The implementation of an aircraft gas turbine engine conceptual design procedure currently being developed under Air Force (AFWAL) sponsorship will result in improved aircraft gas turbine designs with which to proceed to preliminary design. Although gas turbine engine performance and weight sensitivities to changes in life are generally not large (due to the logarithmic relationship of life to stress), past conceptual efforts have not quantified these trades. This is primarily due to the complexity of existing life prediction techniques and the associated detailed design information required by these techniques. A methodology is being developed which will quantify these life/performance trades cost effectively, on a relative basis, via computerized design procedures. Critical to the methodology is an accurate detailed engine utilization definition, which was not known in past efforts. Future conceptual efforts will be enhanced by the addition of life analyses of critical rotating components in the traditional solution of the aircraft and engine interactive design problem.