Help creating "corridors"

I have a problem and no idea how to solve it...

So, for everyone knowing general aviation, I'm trying to define the 
GAFOR-Routes of Austria and Switzerland.
 From the internet site of Austrocontrol (general aviation portal for 
Austria) I have a detailled description for these routes, but only "for 
human beings"...
Something like:

10 LOWI - Mieminger Plateau - Fernpass - Reutte - Pfronten - EDMK 4700
11 LOWI - Inntal - Landeck - Arlberg - Feldkirch - LOIH 7000
12 LOWI - Autobahn A12 - LOIK 2600

and so on...
LOWI, EDMK, LOIH, LOIK are airfield (ICAO codes). Of course I have the 
coordinates of these airfield.
And I have the coordinates of the cities, too.
I think, in OpenStreetMaps I can get the coordinates of other points 
(eg.: Mieminger Plateau).

So, now the problem: I need to create a "corridor" over these regions. 
Then I have to export the coordinates as GeoJSON to display the 
corridors with Leaflet.

And, as I sayd, I have no idea how to start solving my problem... ;)

Thank you very much for your help!
Luca Bertoncello
([email protected])