In response to Jippie's post, and to use Germany as an example, there are a number of German Loco's operating to/from mainstream airports such as CGN and DUS, meanwhile there's an Irish tin pot operator operating to/from a village airfield named Hahn!
Last year I needed to get a guy from DUS or CGN area to FCO and back, I checked the LoCo's from Dus, CGN etc. and guess who the lowest cost of the carriers was? ..... Swiss from DUS!