Note: Distance calculated as road distance.
Airports require a significant footprint to account for current and future operations. Some airports are now close to one hundred years old, and the older an airport is, the more likely it is to be located near the center of its metropolitan area. This relation is far from perfect because of the 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 Also, many older, close-in airports have been replaced by suburban facilities.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. Among the worst cases are Narita and Incheon airports, which respectively service Tokyo and Seoul, but are 66 and 69 kilometers away from the CBD. There were simply no other suitable sites closer.