guys,
What do you mean by "busy"??
Of course Atlanta airport is busy..or LAX or whatever other major hub.
I think the difference between the US and UK is that in england, restricted SPACE is a factor.Many more different control zones,airfields within a very short distance.In the US..lots of room(uncontrolled airspace)between main airports.
I think its clear and easy or is my english that bad?
M.85