THE ash cloud from the Chilean volcano has wreaked havoc across the Southern hemisphere, grounding certain flights in and out of at least 10 Australian cities as well as Cape Town, SA. But why is it that certain airlines choose not to operate in these conditions while others continue to fly?

The decision to fly, authorities say, depends on the altitude at which the cloud sits – over 42 000 feet is not problematic – and the density of the ash cloud – the more dense the cloud, the more risk there is of volcanic metal particles melting and damaging aircraft engines.
 “One of the lessons learned from the first Iceland volcanic eruption was not to summarily close the airspace as was done last year but to provide as much information as possible on ash concentration levels and the coverage of the cloud to enable the airlines themselves to make an informed decision on their operations,” says AASA ceo, Chris Zweigenthal.

“Air Traffic and Navigation Services (ATNS) obtains information from the weather service and the ash cloud monitoring service in Toulouse, France. They then pass it on to the airlines,” says Solomon Makgale, Acsa’s group manager of corporate communications.

“Like in any weather related situation, the airline makes a final decision in view of its unique circumstances.”

Heidi Brauer, Comair’s executive manager of group marketing, says the airline receives regular updates from various control centres locally and internationally, which help guide the chief pilot and his team in terms of decisions regarding safety to fly. “Our approach since Saturday (June 18) has been to consider cancelling night flights (when crew are not able to see any threat), when the alert from the international centre is above a certain threshold.”

In addition, the Comair crew has uploaded additional contingency fuel to permit large lateral detours and earlier descents to keep below any observed ash clouds, says Heidi.

Michi Messner, Qantas Airways’ regional manager for Africa, says: “Since the Puyehue-Cordeon Caulle volcano eruption, a dedicated team within Qantas has monitored its movements to establish the risk to flights.  

“We have a Bureau of Meteorology expert permanently based in our operations centre and we are working closely with the Volcanic Ash Advisory Centre in Darwin and the International Civil Aviation Organisation.”

The airline’s policy is not to fly into areas where the concentration of volcanic ash is unclear, Michi says. “Without certainty about the density of the ash, we do not consider it safe to fly. I cannot emphasise enough that safety is our number-one priority.”