The overly simplistic approach to assessing hazards can be very costly and dangerous. The disastrous consequence of overly simplistic interpretation is perhaps best explained by the recent Iceland volcanic eruption that shut down Europe’s major airports for more than a week. The airport shutdowns cost billions of dollars to the airline industry and impacted millions all over the world.

Since the incident of engine failure on flight BA09 24 June 1982 due to volcanic ash thrown up from the eruption of Mount Galunggung, approx 180 km from Jakarta, it has been an aviation safety rule not to fly over erupting volcanic ash clouds. Thus when Iceland’s Eyjafjallajokull volcano erupted on March 29 and the ash cloud spread all over Europe, the aviation authorities automatically shut down air traffic over European airspace, throwing the world into turmoil.

Six days after the total shut down, reconnaissance flights showed almost no significant effect of the ash clouds on the engines. As scheduled flights return to normalcy, thousands who had been seriously affected would be wondering whether the total airport shutdown was even necessary. What gives?

In order to answer the question, the volcanic ash plume that caused the 1982 engine failure should be examined more carefully with regard to the following points:

- Flight BA09 flew over the volcanic ash plume within the hour of the renewed eruption and the flight path was just 160km from the volcano. In contrast, the ash clouds over Europe are thousands of km away from the volcanic eruptions in Iceland. This in essence means the ash particles are much smaller as the larger and more damaging ash particles would have fallen back to ground closer to the source.

- The density of the volcanic ash is also in question. Europe is more than 20 times in area size compared to Iceland. The ash over Europe would have spread very thin. In contrast, flight BA09 flew over an almost vertical column of volcanic ash within the hour of the eruption. There is probably a critical density and travel distance before the jet engines get clogged up. If the flight paths can be preplanned to keep below the critical density and distance, it would probably be safe to continue flying.

- The ash clouds over Europe are likely to be confined within a certain strata of the atmosphere ie. more laterally spread out than vertically distributed. However, the meteorological satellite imagery would detect the lateral extent but not the vertical thickness; thus giving a more alarming picture than it really is.

The above key factors can easily be determined with some meteorological research and measurements. The aviation safety rule of not to fly over erupting volcanic ash clouds should be modified to include the decreasing risk radii from the source point as well as the risky levels the ash clouds are likely spread over.

It is unlikely that satellite imagery can determine the thicknesses of these ash clouds. Some geophysical techniques need to be adapted to measure the thickness and density of these ash clouds.

Only then can the world travel safely without another global disruption from future volcanic eruptions. We cannot stop the volcanic eruptions but we can sure make our interpretation of the hazardous conditions safer and less costly.

This is a perfect example of ‘a little knowledge is costly and dangerous knowledge’ which of course resulted from an overly simplistic interpretation of a true event – the engine failure of Flight BA09.