Integrated optimization of maintenance interventions and spare part selection for a partially observable multi-component system

•We study an integrated maintenance and spare selection decision for a multi-component system.•We propose a POMDP model since the components exact deterioration levels cannot be observed.•The value of having full information reduces when the correlation between components degradations increases.•The corrective policy is costly when the components deterioration rates are different.•The preventive policy is costly in case the emergency and replacement costs are high.