Vigilance for safety must continue in order to meet the projected increases in air traffic capacity and realize the new capabilities envisioned for the Next Generation Air Transportation System. Present engine monitoring systems consist of vibration sensors that measure damage to the engine after it has occurred. This monitoring system measures a significant cause of this damage as it progresses to provide an early warning of impending damage. The unsafe operation and high costs associated with surprise failures and unscheduled emergency maintenance procedures can be reduced substantially with the use of an in-service life monitor. The accurate prediction of remaining service life will diminish the need for unscheduled maintenance procedures for aircraft with heavy service loads by calling for more frequent servicing of these engine systems. One potential application for this technology is in the U. S. Army Vehicle Technology Directorate for a fleet of helicopters. The U. S. Air Force is another potential end user. We have received assistance from Rolls-Royce and have entered discussions with Honeywell Aerospace for possible applications on their engine systems. NASA GRC is currently pursuing an overall agency-wide goal to increase flight safety of commercial aircraft as part of the NASA Aviation Safety Program. This Program intends to conduct research to improve the intrinsic safety attributes of future aircraft using new and innovative airborne detection methods. In pursuit of this goal, this proposal applies analytical life prediction codes currently used to predict the service life of aircraft engines in the design stage to in-flight on-board monitoring systems that can track the fatigue life usage of specific aircraft. This fatigue-life use knowledge will help to eliminate a safety-related technology void in the maintenance needs of specific aircraft engine systems. By adding airborne detection and monitoring of in-flight fatigue use, NASA and industry can cooperatively achieve increased flight safety goals through a better understanding of the service life of aircraft engines. This effort will provide industry a mechanism to improve the safety, reliability and maintainability of commercial aircraft.