Airports and Urbanized Areas

When it comes to airport enplanements, (as with most count data) the distribution is skewed: A very small number of entities represent a large portion of the total. When it comes to airports, a very small number of airports are 'primary commercial service', meaning that the airport represents more that 1% of all passenger enplanements in America. The other day I read that there are only 17 of them, (with the rest of the 508 commercial airports making up the total [1]). 

Much is said of mega-regions and mega-region planning, but if we really want to talk urbanized areas, we need to talk travel-sheds. (Metro areas are often flawed because inclusion is done on a county-level basis). Suggests to me that we start defining urbanized area by drive to airport.

My wife's parent's would sometimes drive from Tehachepi to Long Beach to pick someone up (about 2 hours and 15 minutes).  

Urban areas get defined by commuter sheds, but in polycentric region, what is within the commuter-shed on one side of the region may not be on the other side of the region. Using airport access as a criterion gets around this particular issue. If you prefer one airport to another, you are within that urban area.

Places with multiple commercial service airports muddy the picture a bit, but might still be delineated as one urban areas, with multiple metropolitan division. 

[1]: https://www.faa.gov/airports/environmental/vale/media/vale_eligible_airports.xlsx