There are at present at least six active volcanoes all around the world that are represented on SIGWX charts.
The only one that unleashed such a response in so many countries is our Icelandic one.
I operated in the vicinity of many active volcanoes in my career, the average no fly zone have always been at maximum a couple of hundred miles from the erupting crater.
And what exactly are those volcanoes? You do understand the huge difference between lava-emitting Italian volcanoes and gas and ash-emitting types such as this one do you? This was on the secondary school Geography syllabus when I was 13 - there are at least 10 different types listed on Wikipedia!
Volcano - Wikipedia, the free encyclopedia