Nom (or lack of it) de Plume

[hairyears]

Well, the trip to Ireland for my father's 80th birthday party was a bust; no flights and an abortive attempt to get to Holyhead overland and take the ferry only served to reinforce my dislike for the town of Crewe

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Further comment...

[hairyears]

The US had first-hand experience of routing aircraft around a volcanic plume when they had less than half the air traffic they do now; and far, far more airspace than Europe.

Our airspace is crowded: spotting a gap in the ashcloud and getting a single flight above the debris, and down again, proves very little beyond the fact that transiting a less-dense region is safe. Admittedly, that's useful information: it means that aircraft can reach a safe altitude, and return, some of the time. But there aren't enough gaps all of the time to fit all of the traffic, and the gaps are a moving target.

Transiting a diffuse part of the cloud is not the same as travelling in it. The documented cases of engine damage involve flying through 5-10 miles of dense ash: is it safer to fly through 500 miles of of diffuse ash - say, 1% of the density of the visible plume? Too many flights are forced by ATC to fly at L200 and L290 when their fuel-efficient altitude is L410 (41,000 feet) - the airlines don't like it but Air Traffic Controllers don't have the airspace to give them in Europe's crowded skies.

So there's less airspace and now we must face the unpleasant reality that there's not enough. Which means fewer flights, and damned expensive tickets.