This research aims to develop and test a practical and precise multi-criteria classification of aircraft spare part inventory management, using the Analytical Hierarchy Process (AHP), in order to maintain aircraft operational availability and to reduce unnecessary downtime. In this study, a multi-criteria model is developed within a large-scale aircraft maintenance and repair firm, in Indonesia. Spare parts data was extracted from the inventory system and analysed to triangulate the model outcome, demonstrate its validity and compare the results against the mathematical results generated by the system's algorithm. The findings suggest that AHP can lead to a transparent, rapid and systematic classification model, this is highly accurate and precise with an outcome comparable to traditional methods. The conclusion proposes that the AHP classification model is more effective and transparent than the currently available mathematical methods. This research contributes to the development of the multi-criteria inventory classification literature in the context of the aviation industry.