Cirium define 'base' as the operational location that the aircraft arrives / departs most often from whilst also factoring in consistent overnight stops from flight activity data.
For fixed-wing aircraft, the derived base location is typically an airfield or airport but for helicopters the location can be a helipad for a hospital or non-airfield private location.
For military aircraft, Cirium defines the base as where the asset is “home-based” so we do not reflect operational deployments.
For any aircraft with status of “Storage” – Cirium reflects the base to be the same as the storage location unless the aircraft is temporarily in a location after an accident. Maintenance centres are not considered to be the aircraft operational base.
For aircraft that do not have a consistent derived base, Cirium does not allocate a base location for example with fractional operators or some low-cost carriers.
The Base fields have typically been used for Business and Helicopter fleets and some military aircraft where this can be determined. Effective Aug-22, you will also see Base location fields populated for some commercial fixed-wing fleets (for data testing purposes at this time).