US airspace system has it sorted.....Quick refresher for those who don't know:
UK A = US B (Most busy airports, LAX, SFO, LHR etc)
UK D = US C (Less busy, but still major airports, SNA, EGHH etc)
UK B = US A (>FL180 in US, > FL245 in UK)
However in the US, most class C areas have a ceiling of around 5000' and most class B areas have a ceiling of 10000' MSL, and combined with this there are often VFR corridors allowing a VFR pilot to 'just fly through' without contacting ATC. Example of this is the LAX VFR corridor, a VFR pilot can sqwark 1201, and head straight through the corridor, directly overhead LAX. Same is true of the class C airports, which although are designated 'less busy' are still VERY busy. Example again is John Wayne (SNA) airport in Orange county, which is probably as busy as Gatwick. Climb to 5001' (I believe, haven't got my chart here) and you can cut straight across the top. One big difference in the US is the use of transponders. To be able to do what I have just described, you need to have a mode C transponder operating (theoretically).
Still there's no reason why IMC rated pilots shouldn't be allowed into airways in the UK, especially if they either have operational mode-c or restricted to a certain FL...
Cheers
EA
