A cloud of ash from an erupting volcano in Chile has drifted over the Atlantic and Indian oceans to lie over southern parts of New Zealand and Australia, prompting the cancellation of dozens of flights on Sunday.
Australian carrier Qantas Airways cancelled 56 flights, including all operations out of Melbourne and the New Zealand hub of Auckland.
"Qantas will continue to monitor the movement of the ash cloud and its impact on further operations," Qantas said. The airline, it said, had "significant experience in managing and assessing the impact of volcanic ash on flight operations".
Air New Zealand had earlier said it was flying at lower altitudes and altering flight paths to avoid the ash, and did not anticipate any disruption.
The volcano in the Puyehue-Cordon Caulle chain in Chile has been erupting for the past week, throwing air travel in South America into chaos, as it spewed ash high into the atmosphere.
Qantas had earlier announced the cancellation of 22 flights, including routes to the island state of Tasmania and destinations in New Zealand's South Island.
"We believe it is just too dangerous," spokeswoman Emma Kearns said.
Air New Zealand said its aircraft would fly at the lower altitude of 18,000 feet (5,800 metres) to remain below the ash cloud or else take a different flight path to avoid it.
The fine particles of ash, which pose a danger to aircraft bodies and engines, were carried east by the prevailing winds to sit between 20,000 and 35,000 feet across southern parts of Australia and New Zealand, said Steve Sherburn, a vulcanologist at New Zealand's Institute of Geological and Nuclear Sciences.
The eruption, he said, was particularly strong and able to keep throwing ash particles in to the atmosphere.
"If the eruption keeps going on, it could affect us for some time," Sherburn said.