Comment by dlcarrier

The optimal airport has two parallel runways, 9,000 feet apart, that align with prevailing wind. If a location has variable strong winds, another set can be built at a 90° angle. It's possible to add more runways at 9,000 intervals, but you're usually better off building an airport somewhere else.

Most airports were built during or before WWII, so few are designed to most efficiently accommodate modern usage. Maybe in the future we can better handle closer runways in low visibility, but first we'll have to figure out how to have two computers communicate directly with each other, instead of having one computer generate routes that get read out load by a human, transmitted over an analog radio, listened to by another human, then typed into another computer.