Pure arse-covering. Backpacker, I'd be interested to hear if there is any reaction from the authorities to the protest; how do they explain closing the airspace to gliders, for example!?
Is there a way to find out who has issued a certain NOTAM? They do not seem to include contact details when looked at through the
Aviation Weather >> Europe > metar taf sigmet notam winds aloft significant weather information site.
Edit: I had a look at the KNVvL site, and the Dutch minister claims that the ban on all flying is due to "possible blockage of the pitot tube". I'm forced to wonder what planet these people live on.