In this paper, we provide an overview of operational spare parts planning in service control towers. We conduct company surveys to identify the issues, the challenges, and the needs in practice. We propose a classification framework to reveal the key aspects of operational planning decisions, and to provide an overview of the scientific literature. We identify promising research directions. These include incorporating service level agreements in operational decision making, managing exception messages, integrating tactical and operational plans, using advance supply and demand information for operational interventions, and developing a unified and holistic approach for selecting interventions in large scale systems.