Note: Distance calculated as road distance.
The older an airport is, the more likely it is to be located near the center of the metropolitan area it serves. This relation is far from being perfect because of the respective geographical differences in the spatial structure of metropolitan areas. Also, many older, close-in airports have been replaced by suburban facilities. An extreme example was the replacement of Stapleton Airport, just 8 kilometers from downtown Denver, by the new Denver International, located 37 kilometers away. The worst cases are Narita and Incheon airports, which respectively service Tokyo and Seoul, but are 66 and 69 kilometers away from the CB. There were simply no other suitable sites closer.