In the last 12 years new conclusions have been reached concerning the traditional reliability model for turbine aircraft engines. The overhaul of engines at one point in time has been discarded. New maintenance processes called “On Condition” and “Condition Monitoring” have been defined. A simple decision diagram has been devised to determine the proper maintenance process for each part. The historical background for these new conclusions, the maintenance decision diagram, and a new maintenance program called Powerplant LIBRA are discussed in this paper.