Many thanks for the suggestions, Allocator. My first thoughts are, and please correct me if I’m wrong:
Suggestion 1 surely works only with aircraft transmitting position information anyway. I want to identify the ones near me that aren’t transmitting it.
Suggestions 2 and 3 are useful, - I hadn’t thought of that Latitude = 0 trick - but at the moment, MyFlights is showing 80-odd aircraft: each suggestion just about halves that, still leaving about 40 possibilities for that anonymous dot in the sky overhead.
Suggestion 3 would require a long ladder, nerves of steel, and athleticism that left me years ago!
For now, I think I still want that gain control.
Any more ideas?
Rod