I fly with the googles often and camino ken is right, the range varies by day/location. Out in the country I'll get 1080p maybe out to a mile, near a town or city is half due to interference.
Not really worth having on though, when you select 1080P transmission the AC doesn't allow 4k filming so I always fly with 720P, doesnt really make much of a difference between the 2 views. I'd rather have a clean 720p connection over a spotty 1080p signal.