You don't actually need radar to have air traffic control. It's just that ATC can't provide tracking services for the entire route. Instead, aircraft file thei

You don't actually need radar to have air traffic control. It's just that ATC can't provide tracking services for the entire route. Instead, aircraft file their routes in advanced (which are either a series waypoints, or a fixed airway), and pilots occasionally radio in position updates as they progress. The airspace is still controlled, but without tracking, the separations are much larger. Any two aircraft that might be on the same route or might cross paths have different assigned altitudes, and they must communicate with ATC before changing altitude or route.