A multi-airport system is the set of airports that serve the airline traffic of a metropolitan area. The multi-airport system for London, for example, includes -- among others -- its major airports: London/Heathrow, London/Gatwick and London/Stansted.

The proper management and development of multi-airport systems are a major concern of airport managers worldwide. All metropolitan regions generating more than 10 million originating passengers a year have several airports serving commercial carriers.

The experience in managing multi-airport systems is poor. It is routinely marked by expensive mistakes. Planners fail to anticipate the patterns of traffic distribution between airports, and managers consequently over invest in second airports, overbuilding facilities for a traffic that is unlikely to be there.

(source: De Neufville (1995))