Material aging is a principal cause for the aging of engineered systems that can lead to reductions in their reliability and continued safety, and increases in the costs of operation and sustainment. To meet the challenges of designing systems for a competitive global market and of ensuring their reliability and continued safety, a new paradigm for design is needed to quantitatively integrate materials aging into the processes of design, reliability assessment and life-cycle management planning. In this paper, a multidisciplinary, mechanistically based probability approach is reviewed as a framework for this new design paradigm. The efficacy and value of this approach is demonstrated through an example on the aging of aluminum alloys used in aircraft construction that showed the feasibility of using a simplified model to predict the distribution in damage in transport aircraft that had been in long-term commercial service. The need and directions for further research are discussed.