By Marcus Leach

An ash cloud from a Chilean volcano is set to cause chaos at Australia's two leading airports as it drifts across southern Australia.

Already Qantas and Virgin have cancelled all of their scheduled flights in and out of Sydney and Melbourne airports, with more set to follow over the coming 48-hours.

The ash cloud has come from Chile's Puyehue-Cordon Caulle volcano, and whilst last week when it was higher planes were able to fly under it, the same can't be done this time as the plume is too low.

With the ash cloud hovering between 20,000 and 40,000 feet, meaning Qantas said its policy meant it was too risky to fly below it.

"We estimate that we will be cancelling in excess of 200 flights on Wednesday," Qantas spokeswoman Olivia Wirth told reporters.

"The experts say we simply won't be able to operate in this situation."

Virgin's cancelations will affect in the region of 120,000 passengers, with further disruption expected to ground flights in Adelaide and Cranberra over the coming 48-hours.

"When you take out major centres like Sydney and Melbourne, the knock-on effects of that are huge, and that's unfortunate, but safety has to come first," Civil Aviation Safety Authority spokesman Peter Gibson said.

"When it's safe to go flying, the airlines will go back, but not until then," he said.

Join us on
Follow @freshbusiness