Thousands of airline passengers endured a third day of delays in Australia on Tuesday as the ash cloud from Chile's volcanic eruptions kept planes grounded.

Qantas and Jetstar lifted a ban on flights to and from Melbourne but services by the two airlines in and out of the southern island of Tasmania, to and from Adelaide and New Zealand were cancelled for the day.

"Qantas will continue to monitor the movement of the ash cloud and assess its impact on flight operations as the situation develops," the airline said in a statement.

"The Qantas Group's approach to flying is based on the highest standards of safety and risk assessment. Safety is always put before schedule."

Tiger Airways cancelled services between Adelaide and Melbourne and Perth and Melbourne.

While Qantas and Jetstar continue to take a conservative approach, Virgin resumed normal flights to Melbourne, Tasmania and New Zealand with its planes flying around or under the ash plume.

They are also flying in and out of Adelaide, as are international services by Singapore Airlines and Malaysia Airlines.

"We have got our own volcanic ash management team which is a team of experts in everything from engineering to navigation and a Bureau of Meteorology person in-house," Virgin spokesman Colin Lippiatt said.

"We would not be operating if we did not believe it was completely safe."

Air New Zealand's domestic and trans-Tasman flights also continue to operate to schedule.

"By adjusting cruising altitudes of our aircraft we are able to continue to safely deliver customers to their destinations," Air New Zealand said.

It added that almost all other carriers with services to New Zealand were operating, including Emirates, Singapore Airlines, Thai Airways, Cathay Pacific and Korean Air.

The eruption of the Puyehue volcano, high in the Andes, has spewed ash that has disrupted air travel on a scale not seen since the volcanic cloud over Iceland paralysed Europe in 2010.

Flights across South America have been hit, with strong winds carrying the ash more than half way around the world, over the southern Atlantic and southern Indian Oceans to Australia and as far as New Zealand.

Andrew Tupper, the Australian Bureau of Meteorology's Volcanic Ash Advisory Centre head, warned the crisis was not yet over.

"I think it's fair to say there will be more disruption, so that's the bit of bad news," he told ABC radio, adding that while the ash was heading back to South America, it could return to Australia.

"It has been known to do a double lap in the past," he said.

Peter Marosszeky, an aircraft maintenance expert and senior lecturer at the University of New South Wales' Department of Aviation, said there could be dire consequences for aircraft flying through the ash.

"The dry nature of ash, mainly pumice stone, acts as an abrasive on all exterior parts of the aircraft, ablating the finished surfaces like sandpaper," he said.

"In addition it will choke up the sensitive ports within the engines and block them.

"Volcanic ash in the air has disastrous consequences on aircraft that fly through the cloud."

Australia's Civil Aviation Safety Authority says it has no issue with airlines flying provided they avoid areas of forecast volcanic ash and any actual areas of ash.

earlier related report
Chile ash cloud disrupts flights on two continents
Buenos Aires (AFP) June 13, 2011 - A volcanic ash cloud originating in Chile delayed flights across South America and Australia on Monday, stranding thousands of travelers and forcing UN chief Ban Ki-moon onto an overnight bus.

The eruption of the Puyehue volcano, high in the Andes in southern Chile, entered a second week, spewing ash that has disrupted air travel on a scale unseen since the volcanic cloud over Iceland paralyzed Europe in 2010.

Buenos Aires airports suspended domestic and international flights on Sunday night for the third time in a week, prompting a crisis meeting Monday to assess the situation, the Argentine Civil Aviation Administration said.

"Meteorological conditions have worsened again, with forecasts that the cloud of volcanic ash will remain suspended in the area over the Ezeiza airport and the Jorge Newbery Metropolitan Airpark," the agency said.

At the Ezeiza international airport, an Ecuadoran tourist anxiously awaited a break in the dusk cloud to fly home for medical treatment.

"We're biting our nails, we're so anxious," she said.

Daniel Alegrin was stranded at the airport after flights to Alicante, Spain were delayed for a week.

"We come from Rosario (Argentina) and the (airline) refused to assume responsibility for our return home on grounds that it was a natural disaster," he said.

The UN secretary-general became the most high-profile person to be stranded after he was forced to rough it on an overnight bus to meet Argentinian leaders on Monday. Worse still -- it was his birthday.

All ended well as Ban, who marked his 67th birthday on Monday, made it to the capital in time to meet Argentinian leaders and win their support for a second term as secretary-general.

"We are very happy to welcome him and to say to him that we support with joy his re-election," said Argentine President Cristina Kirchner.

However aviation authorities in Buenos Aires re-opened the city's two main airports at 9 pm (0000 GMT Wednesday).

"The cloud of volcanic ash ... has diminished its intensity and reduced its impact, and the forecast is for the rest of (Monday) as well as the early hours of (Tuesday) it conditions will be favorable towards flying," the National Civil Aviation Association (ANAC) said in a statement.

Montevideo's Carrasco international airport in neighboring Uruguay however was still suspending operations, with more than 85 flights cancelled, officials said.

The flight disruption affected Peru's visiting president-elect Ollanta Humala, who canceled a late Monday dinner meal with Uruguay's President Jose Mujica and boarded a ship to Buenos Aires for the next leg of his trip. He had originally planned to leave Uruguay on Tuesday.

The Chilean Meteorological Service said prevailing winds would continue to blow the ash into Argentina through Wednesday.

Chilean seismologist Enrique Valdivieso said the eruption could run its course within a week, but it was hard to know based on precedent. An eruption in 1960 lasted two weeks, but an earlier one in 1921 lasted two months.

The June 4 eruption has been hardest for tourist areas near the volcano like the alpine resort of Bariloche, whose airport has been closed for a week, and Villa Angostura, which is 30 kilometers (18 miles) away.

Strong winds have carried the ash cloud half way around the world, snarling travel as far away as Australia.

The eruption in 2010 of an Icelandic volcano, Eyjafjoell, caused the biggest aerial shutdown in Europe since World War II, affecting more than 100,000 flights and eight million passengers.

Puyehue's eruption sent columns of debris 10,000 meters (six miles) high, blanketing the picturesque mountains and lakes along the Chile-Argentina border in a snowy white ash and prompting the evacuation of 3,500 people.

Its last major eruption was in 1960, following a 9.5 magnitude earthquake -- the largest on record.