Maybe what I'm doing is something like that. When I come up on a sunken airfield now I have been pausing, then pressing Alt W S and go into the library, Then open Vector and then finding the ICAO for that strip, disable it and then go back to the FSX library and press OK to update the airfield. It's the only thing I've found that works, it's just that it's time consuming and at 72 time is at a premium