Volcanoes, Airplanes and Quantifying Risk

On April 19th, 2010, IATA, the chief trade group representing airlines, issued a press release which states in part: “IATA criticized Europe’s unique methodology of closing airspace based on theoretical modeling of the ash cloud. ‘This means that governments have not taken their responsibility to make clear decisions based on facts …’ said [Giovanni] Bisignani [IATA’s Director General and CEO].”

This statement leaves the unfortunate impression that decisions based on theoretical models are somehow suspect and of little value.  The better, but less soundbite-friendly, question should have been whether the model adequately predicts the risk. To make useful predictions, a model needs to do two things:

  • account for all key factors that influence the outcome
  • quantify how each factor influences the outcome.

To the frustration of passengers, airlines and businesses around the world, the eruption of the Eyjafjallajokull volcano in Iceland presented several challenges for modelers.  Some of the key factors playing a role here include:

  • Ash composition: how damaging is it?
  • Extent of the cloud: how high, how far and where?
  • Aircraft capability: how much ash exposure can airplanes handle?
  • The costs of staying grounded vs. the costs of catastrophic failure

These four bullets of course represent just the tip of the ice berg: each of them summarizes a long list of related factors.  For example, while current data is unavailable, scientists have to rely on past experience when estimating the size and weight of ash particles, their chemical make-up and the density of the ash.  To confound matters, predictions regarding wind speed, direction and turbulence need to be considered as well.

So the real question needs to be: how well does the model represent the current situation? How well do we understand what the actual key factors are?  How well can we measure them?  Are we relying purely on past insight or can we refine our knowledge with data from the current situation?  To what extent can current satellite images, air samples and meteorological measurements improve our ability to predict the risk to life and well-being of people and property?

This interactive map on the BBC we site shows one example of how output from such modeling looks by mapping the extent of the plume over several days along with normal flight routes across the Atlantic.  This post in Business Week sheds some light on our spotty knowledge regarding the real risks of volcanic ash.

The other critical question revolves around acceptable risk.  Risk not only originates from ash clouds. It also comes from “playing it safe.”  Billions of dollars in lost revenues and productivity put the livelihood of hundreds of thousands of people at risk.  Every day we accept the risks of driving our car – so at what point do ash clouds represent a higher risk than driving a car?  Even if we could come up with an exact numeric value for these risks, how does the value of human life fit into these equations?

Therein lies the apparent disconnect between statistical models and real life: intangible values sometimes outweigh what can be measured.  The decisions we make depend on how we actually perceive the risk.  Yet, in order to put our perceptions into perspective, we need to have good numbers to guide us – and getting good numbers requires a good model of reality.

So, before we start talking about law suits, we need to accept that risk is inherent to anything we do.  Blaming people for doing the best they can to balance public safety with economic considerations wastes resources that would be better spent on improving our ability to assess and manage risks.  We send unmanned drones to gather combat intelligence, why not modify them to collect air samples?  Why not fund research to create better models for volcanic plumes? Especially if history should repeat itself and Eyjafjallajokull continues to sputter for the next year or two.

Additional Reading

From Eruptions, a blog dedicated to volcanism:

Airlines lobby to reopen European airspace closed by Eyjafjallajökull
Posted on: April 18, 2010 2:30 PM, by Erik Klemetti


Eyjafjallajökull flight cancellations: How the right decision is being made to look wrong

Posted on: April 22, 2010 9:40 AM, by Erik Klemetti


Research Gap Left Airlines Exposed to Volcano’s Blast (Update1)

April 22, 2010, 9:05 AM EDT


Is driving more dangerous than flying through ash?

Page last updated at 10:51 GMT, Wednesday, 21 April 2010 11:51 UK


Could aircraft dodge the volcanic ash cloud?

Page last updated at 14:06 GMT, Tuesday, 20 April 2010 15:06 UK

By Stephen Mulvey

BBC News


Recriminations erupt in ash-fueled aviation crisis

AP 4/21/2010

By Arthur Max, Associated Press Writer


How volcanic ash could ground your next flight

By Larry Dignan | Apr 15, 2010


How Volcanic Ash Can Kill An Airplane

Apr 15, 2010 09:00 AM

Ray Wert

Story & pictures of KLM Flight 867


Iceland Volcano Vs Mt. St. Helens And Airspace

Pilot’s discussion forum


Volcanic Ash Contingency Plan

ICAO (International Civil Aviation Organization)



MD F.E. Bustillo Iii MD F.E. Bustillo is a 3rd degree contact

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2 comments to Volcanoes, Airplanes and Quantifying Risk

  • Claudia,

    thank you for your comment and implied question. You are right: it appears that better communication and coordination would have made this episode less frustrating to everyone concerned.

    What makes these events also applicable to Six Sigma is the Catch-22 between “lack of data” and “defining the problem.” In the Define phase of DMAIC our challenge is to understand and agree on the parameters that allow us to quantify the problem and measure progress. When we deal with routine situations, we have industry norms and best practices to guide the problem definition. Things get interesting when knowledgeable people disagree about what the norms and best practices should be. In this case, some people felt the need to be conservative in the name of safety, while others preferred to assess the risk in less stringent terms.

    A successful Six Sigma project leader needs to be able to harmonize conflicting needs and priorities in order to complete the “Define” phase. Often data can help, but there are times when stakeholders disagree on what the data means and how it should influence our actions. To me the Eyjafjallajokull eruption is a case study of how difficult “defining the issue” can be.

  • Claudia

    My sister was caught in Ireland during this most recent eruption. It got me researching the techniques that the IATA used to determine what was safe and what was too risky. All very interesting and I can see why they held off hundreds of flights – really they would have gotten worse press had they “allowed” a plane to crash.

    Not sure why this was linked under six sigma or how six sigma methodology could have made much of a difference (though better communication may have), but you’ve provided some good links.