Want to get somewhere and don’t know which airports connect to which places? flightconnections.com does it. It does not deal with connections between airports, most likely because that is an engineering problem that they do not want to deal with, but it is already a very helpful tool.
I used it to investigate how to get to the airport in Wales, Alaska (by way of Anchorage) in order to take a boat to Naukan, Russia. It’s only about fifty-five miles across the Bering Strait:
Technically, Diomede, the island between them, is Alaskan. Therefore, the shortest distance between the US and Russia is only about twenty-five miles.