Accountability?
Isn't the problem here about accountability anyway?
IFR Class A airspace aircraft are 'controlled' by someone who cannot verify that there is not a dense ash cloud on the route in the path of the aircraft - therefore he cannot be expected (individually or corporately) to give a clearance ...
... the pilot would be able to determine if his path were obscurred by dense volcanic ash - but he is (effectively) not allowed to look out of the window in Class A airspace. (No VFR or SVFR in Class A Areas)
Temporary permission to fly SPECIAL VFR in Class A Controlled Areas - could help.
I guess most of the UK population is looking up at the sky and not seeing a volcanic cloud at all - 8/8 blue?
Can anyone see this cloud ?
Is it just a theoretical possibility which is being avoided?
Can this possibility be verified....?
Is there an observable upper atmospheric dust cloud somewhere?
Am I missing something here?
Is there damage from invisible trace ammounts ?
Are we talking about parts per 10 billion?