All answers so far are relevant to the US only...In other countries VFR flying is prohibited above a set altitude, for example 2500ft.This because the IFR traffic is as thick as mosquitoes in a swamp and having some Cessna buzz them just wouldn't do.

This thread has turned out to be as informative as I'd hoped it would be. Thank You all for your input. :-wave :-wave :-wave Will

What countries are you talking about ? I think you MAY be referring to the airspace around London which is class A above 2500 feet.This means that aircraft operating in the small airfields around London have to remain at 2400 feet until clear of the zone.But this is the same with any class A airspace.I have never heard of a country where VFR is not allowed above 2500 feet :-)Peter