I remember working on an overlay for air base ranges back in the first Alpha world, but with three ranges per air base and a bunch of air bases on the world, it got convoluted really quickly!
I'm thinking I can maybe play with a highlight that appears when you hover your cursor close to an airbase (either in the world view or perhaps in the Air Base tool from the world view).
In the meantime, though, do you have a keyboard shortcut set for the Ruler tool? I find using that from an air base or target works pretty well.