What is the altitude at which planes "drop off" radar in that area?
"What is the altitude at which planes "drop off" radar in that area?"
Good question. Not got the fainest idea to be honest. I kind of always assumed that, at that proximity to an airport, it would be impossible to be in the air at any height and the controllers not to be aware of it. I had a quick read about airport air traffic control systems on Wikepedia which seems to mesh with that:
http://en.wikipedia.org/wiki/TRACON
"Typically, the TRACON controls aircraft within a 30-50 nautical mile (56 to 93 km) radius of the airport between the surface and 10,000 feet."
I'll happily defer to anyone with any expertise on this however.