Structural aging under fatigue loading is one of the most common failure mechanisms in civilian structures such as composite bridges, power lines, and composite ship structures. The developed probabilistic fatigue life prediction tool can be used effectively and efficiently to assist a designer and rule maker to answer the following questions: 1) How tolerant of cracks is the location? 2) How long to repair a crack in service? 3) What is the impact of an operational profile change? 4) How often should inspections be made? and 5) How can SHM input be used best? The tool can be used to assist commercial and military industries to reduce the cost of test-driven design and process iterations with the use of the virtual testing tool. Finally, teaming with Boeing, a highly visible airplane manufacturer, will considerably shorten our development cycle from producing a prototype research orientated tool to commercially accessible design software. The results from this research will have significant benefits to enhance the aviation safety program in the NASA. It will result in: 1) a commercially viable, accurate, computationally efficient, and user-friendly probabilistic residual life assessment tool for charactering delamination crack growth and perform damage analysis with the presence of uncertainties in design and loading parameters; 2) an integrated analysis framework for fatigue damage prognosis and health management of composite aircraft structures; 3) a virtual testing tool to reduce current certification and qualification costs, which are heavily driven by experimental testing under various stress conditions; and 4) innovative probabilistic methods and reliability assessment procedures to facilitate the condition-based maintenance and reducing unscheduled maintenance.