This thesis involves a case-study of aircraft engine combustor maintenance at KLM E&M, which has been used as a basis to develop a discrete event simulation model that allows TAT to be measured, and the effects of changes to the main process value drivers to be successfully tested. The main research question this research sought to answer is: What are the value drivers that determine the turnaround time of the aircraft engine combustor maintenance repair and overhaul process from a Lean Six Sigma perspective? From literature and preliminary research it was possible to identify TAT value drivers and define performance criteria. The main value drivers have been found to be capacity, capabilities and components. Planning and routing have been defined as influential factors that aid in steering the process. In order to come to this answer the current state of combustor maintenance at KLM E&M has been analysed, using the Six Sigma Define, Measure, Analyse, Improve, Control (DMAIC) framework. A conceptual framework including the value drivers was developed. Using this framework and Lean Six Sigma tools the combustor maintenance process has been analysed in order to define the main relationships between value drivers, as well as the current state performance at KLM. In order to simulate the process and test the effects of changes to the value drivers the current state process was modelled in Simio. Using this model it has been possible to define TAT and to test the influence of the value drivers. This has lead to recommendations regarding how TAT can be reduced.