The aircraft operational availability, dispatch reliability, maintenance history, and maintenance plans will drive the actual spares and tools requirement. The initial spares and tools provisioning is typically configured for the first year of operation and has to be monitored and adjusted over time, and in some cases also reassessed with regard to regulations and contractual obligations.

Sometime within the first year of a new operation the patterns will be well established and the historical data can be used to determine the requirements for the next period. Also, as the flying hours increase, parts and tools requirements for support of major maintenance will have to be addressed.

ACS can reassess and recommend changes to the spares pool at defined intervals.