This is beginning to look like the blind leading the blind leading the blind.
If you study the six-hourly actual/predicted 'ash cloud' source map data from the London VAAC that is being published by the Met Office and allegedly being used by NATS to make its UK Controlled Airspace open/closed decisions, you can see from the predicted data yesterday exactly why they chose to open the Scottish FIR and nearby regions, albeit temporarily, today. However, the maps are all clearly marked "ASH CONCENTRATIONS UNKNOWN".
If the ash concentrations are unknown then how is it possible to define the edge of the contaminated area where presumably the ash concentration has supposedly fallen to some identifiably small but as stated "UNKNOWN" level in the first place? What is that level and how does the VAAC even know where to draw the line?
Further, this apparently unknown concentration region of ash extends throughout most of Europe where flying has been permitted today.
NATS is clearly basing its fly/no fly decisions precisely on these maps and the livelihoods of large numbers of people around the world are being substantially impacted by this extremely ill-defined and completely misleading information.
Someone needs to be brave enough to step up and stop this madness. Everyone is hiding behind data produced by a group of well-meaning technical staff at the London VAAC but not being prepared to make a common sense decision as the stakes of making that call are astronomically high if wrong!
It does appear that the Europeans have been prepared to stick their necks out well before our politicians/bureaucrats have.