“Volcanic ash can be dangerous for aircraft, causing damage, reducing visibility, and potentially clogging engines” and so there are currently no flights over the UK and much of Northern Europe.

At 8.20 tonight the NATS site said ” restrictions will remain in place in UK controlled airspace until 1300 (UK time) tomorrow, Friday 16 April, at the earliest.” and “at 0230 (UK time) tomorrow we will advise the arrangements that will be in place through to 1800 (UK time) tomorrow. However be aware that the situation cannot be said to be improving with any certainty as the forecast affected area appears to be closing in from east to west.”

As I walked through London I overheard conversations between worried tourists and businesspeople, but also jovial banter about people stuck on holiday in the south of France.

First question then is for the vulcanologists and meteorologists:

“How long will the cloud of ash stay over the UK?”

Answer is of course “We don’t know, no really, we don’t” – it depends both on the length of the eruption (it’s still going on) and on the weather conditions.

So it could be over in a few more hours. Or it could go on for months (!) Thor Thordarsson is quoted on BBC news as saying: “If the eruption has a face change and starts to produce lava… then we might be in for a much longer haul, an eruption that might last for months or even years, with a quiet period in between intermittent explosions.”

Prof Bill McGuire, professor at the Aon Benfield UCL Hazard Research Centre is quoted in the same article: “it is worth noting that the last eruption of Eyjafjallajoekull lasted more than 12 months.”

That was 1821-1823 though – no jet engines to damage.

So more questions, this time for economists. In the case where the eruption continues for months:

1. What is the daily economic effect of a total ban on airtravel in the UK? (I normally hate these big numbers bandied around, but if we can do it for snow hitting London, we can make an estimate for this) What are the costs? Missed meetings, people just not being in the right place at the right time, delayed delivery of cargo etc.

2. How about that for those countries that are currently affected by the cloud?

3. How long can airlines stay in business in the face of no air travel? Are we talking days, weeks or months? When might we expect the first call for a government bail-out?

4. Which are more vulnerable to a prolonged ban, airlines or the airports?

5. Which other businesses in the air travel value chain will be seriously affected – who is highly dependent and already economically weak?

6. Who’s going to make a killing, other than Eurostar? or (gulp) the ferries?

Note: these questions are not all mine, they have came up in conversation with fine Tuttle people in the course of this evening.