Through the lens of aerotropolises...cities with airports at their urban nucleus.

http://www.aerotropolis.com/files/Trade_Transportation_SpatialDistribution.pdf

http://www.aerotropolis.com/files/1988_19_spatial_processes.pdf

You might look here for a function with easy-to-estimate parameters . . . based to a degree on central place theory:

https://www.researchgate.net/publication/230505064_Central_place_theory_and_the_simple_economic_foundations_of_the_gravity_model

Article Central place theory and the simple economic foundations of ...

An airport may function as  a central place within the global system of center.It may cater the complementary areas around within or extra boundary  areas of the country of location.The linkages with other service functions   will determine the central position and hierarchy of the centers.

There is probably a system of rating airports and their functions, e.g. general, international, etc so you can rank the importance of that airport and see how much traffic it will attract compared to other airports.  Then look at the nearby areas to see what commercial functions they currently have and which are dependent on the airport, e.g. trucking, warehouees, etc. commercial mail, etc. then go from there.

Quite aside from the excellent suggestions already made, you will likely want to distinguish the types and volume of aircraft served (local general aviation vs. comprehensive commercial passenger jet) not only in the speed of the aircraft (spacing of airports being a function of temporal and economic distance), but also the variety of services found in them, the ground transport access to them, and the air traffic control systems deployed for commercial air transport. You get a sense of this looking at .