An ash cloud created by a volcanic eruption in Chile more than two weeks ago has prompted at least one Australian airline to suspend flights again after the plume looped the globe and returned Down Under.
The Puyehue volcano's activity has been steadily decreasing, allowing people to return to their homes in the Andes mountains, but the huge ash cloud it ejected is still floating over the southern hemisphere.
Virgin has suspended all flights in and out of the South Australian capital Adelaide on Tuesday, as well as the regional town of Mildura, due to the ash, and said it was watching the situation in Melbourne and Tasmania.
National carrier Qantas has not yet announced any cancellations, but the airline said passengers could face delays in Adelaide early on Tuesday.
"It will obviously cause disruption, it will obviously prevent aircraft flying at the altitude of the cloud," Andrew Tupper, head of the Australian Bureau of Meteorology's Volcanic Ash Advisory Centre, said of the plume.
"How they (airlines) choose to cope with that is their decision."
Tupper said the cloud was about 2,000 kilometres (1,200 miles) south of Western Australia, but was expected to cross the southeastern coast and affect Adelaide early on Tuesday. It is also likely to affect Melbourne, he said.
He said while the ash had thinned during its travels around the globe it was still clearly visible on satellite images and was travelling at an altitude of 8-13 kilometres, generally cruising level for aircraft.
"Although much of the ash that came around us last week has dissipated the leading edge of it... is coming around for another shot," he said.
He added that it was too soon to know whether it would affect the country's busiest airport Sydney, but admitted the cloud would be an "uncomfortably close" distance of about 100 kilometres from the hub.
The cloud entered Australian and New Zealand airspace just over a week ago, causing some airlines to ground all flights to affected areas while others chose to divert their planes under and around the plume.
The ash disrupted the travel plans of tens of thousands of people in Australia and New Zealand, cancelling some travel across the Tasman Sea and affecting flights to Melbourne, Adelaide, Perth and Hobart.
Tupper could not say how long the new ash front would last, but said it would probably linger over any one place for only a day.
Ash poses a significant threat to aircraft because once sucked into engines it can be converted into molten glass as a result of the high temperatures and potentially cause an engine to fail.
Virgin Australia said flights to and from Adelaide and Mildura would continue until the last services on Monday, but forecasts that the ash plume would be below 20,000 feet over those airports on Tuesday had forced the cancellations.
"Our main focus for the near future is looking at Melbourne and Tasmania," a spokesman for the airline said, adding that the chance of the ash affecting Sydney were a lot lower than airports further south.