An aircraft engine is a complex and advanced system with high demands on safety and reliability. Maintenance and how it is performed is therefore of outmost importance. Each maintenance occasion must be as effective as possible and execute the maintenance needed without performing excessive maintenance. A previous research project has developed an optimization model to calculate the optimal balance between the remaining lives in engine components and the cost related to each maintenance occasion. A potential to further improve the optimization using the model has been identified if the life-length of all the components used can be estimated. Hence, the aim of this paper is to describe a research challenge on how to develop a framework for estimation of the remaining life in aircraft engine components and by that group the components in different life-length classes.