This thesis investigates how KLM Engineering & Maintenance can integrate circularity into aviation MRO decision-making to retain value in parts by redesigning how routed-part outcomes are made visible, comparable, and steerable in daily work. The research is grounded in part routing in the Salvation & Warranty context, where parts move through a sequence of gates under contractual, technical, and operational constraints, and where circular value is often lost.

A qualitative case-study design was applied, structured through five sub-questions that move from reconstructing the as-is routing system and decision funnel to defining and operationalising circularity at part level. Data collection combined semi-structured interviews across roles, follow-up clarification meetings to validate the evolving routing map and gate logic and a co-creation workshop to test indicator feasibility and shared understanding under operational constraints.

The thesis contributes a set of design requirements for circular routing decision-making, a linked indicator system that operationalises circular value retention through routed-part outcomes (R-levels) and adds steering and prioritisation layers (R-ratio trend steering, Functional Lifetime Loss based on benchmark service potential, and an indicative CO₂ effect based on internal carbon assessment factors) and a staged implementation roadmap in three horizons that separates foundation building (shared language), stable logging and steering, and long-term embedding through governance and an external repair ecosystem. These deliverables were brought together in the form of an interactive website to make it workable and distributable for KLM E&M.