I prepare titles in the Northern Virginia counties and as such do a lot surrounding Dulles Int airport in Loudoun county Va- most of the subdivisions that are in the flight path incorporate an "avigation" agreement in the chain of title and applies to all the land in the subdivision, If anyone would like a copy of one of these agreements to review- drop me an email and I'll be glad to send along a copy for you to read.( I can't add  a link since the county site is a secure site and password protected , but for those that have access to this county- it is in DB 1492/2387- this is also for all those that are good enough to be able to hack into online systems so they don't have to waste their time looking for an example themselves !)
Steve Meinecke