I flew back and forth from the US to Asia for several years, like many other pilots. Warnings (sigmets) for volcanic ash were and still are commonplace in Alaska and the Kamchatka peninsula in Russia's far east. The US nor the Russians closed their respective airspace. You re-route and carry more fuel.
Of course flying through volcanic ash is not wise, but to do the "blanket approach" and shut down airports and airspace that is not infected by the ash, is incredible.
This is going to set the airline recovery back another century. Get ready for thousands more qualified and current pilots to join the ranks of the unemployed if airlines are unable to cope with this economic setback.