Substantial growth in air travel has put considerable pressure on airports to increase their capacity to cater for this increasing demand; for example, by expanding terminals or building additional runways. Air transport in Asia-Pacific has been growing at an unprecedented pace, such that it now has the largest share of total world capacity out of all other regions. The foregoing factors describe dependency in an airport context. Dependency is defined as the quality of being decided by something else. In Asia-Pacific, the Australian case of Cairns and Darwin airports illustrate the country- and city-specific dependence issues well. The variation in dependency according to these changes was also successfully reflected in the airport dependency index (ADI) and was consistent with industry observations, hence showing the relative Gini-based ADI as a robust measure of dependency. By measuring and quantifying dependency, the ADI provides information to assist the formulation of air transport and regional development policies.