Airport modelling has concentrated on specific subsystems of the airport complex, such as the landside (terminals), the airside (runways and taxiways) and the access/egress system (roads, parking, etc.). However, users must manually co-ordinate inputs and outputs for the various models in order to account for the interaction between the airport subsystems. Similar co-ordination is required for users to mix strategic models (usually involving a low level of modelling detail) with tactical models (requiring a high level of detail in data and system definition).