Aircraft maintenance is inherently unpredictable due to differences in failure rates between components. This results in high variance inflow in repair shops, which in case of insufficient capacity yields long turnaround times and thus the need for additional components in stock. The aim of this research project is to determine the effect of service level optimisation in the presence of highly variable demand from an aircraft maintenance supply chain perspective. The first approach focuses on determining the optimal capacity in the repair shop using a greedy algorithm, while the second aims at controlling demand by assisting in in- or outsourcing decision-making by means of a multi-criteria decision-making model. A case study at KLM Engineering & Maintenance is performed to test the applicability of the models in the aircraft maintenance industry.