Flights across Australia began returning to normal Thursday after days of travel chaos from the Chile ash cloud, but some services to New Zealand remained grounded.

Qantas, Virgin and Jetstar were all planning to resume flying to Perth and Tasmania, routes that have been badly disrupted by the ash from the erupting Puyehue volcano, high in Chile's Andes.

Airservices Australia spokesman Matt Wardell said the ash was dissipating and flights should be fine for at least the next 48 hours.

"The long-term prognosis is still a little uncertain but at least for the next couple of days we are looking at being able to resume normal services," he told reporters.

"It may take us a day or so to get the entire air traffic back to normal operations, but for the time being things are looking pretty good."

But with the plume detected at lower levels than previously recorded in New Zealand, Qantas once again cancelled all flights to its southern neighbour, as well as to the Argentinian capital Buenos Aires.

"Qantas is urging all customers to reconsider any non-urgent travel and defer their travel plans wherever possible," the airline said.

Virgin, which had previously opted to continue most of its New Zealand services by flying around or under the ash, suspended flights into and out of Auckland and Hamilton.

Like Virgin, Air New Zealand had been bypassing the ash but it was forced to call off many domestic services Thursday, with the cities of Christchurch, Dunedin and Invercargill affected.

Two international flights from Christchurch to Australia were also cancelled, while Singapore Airlines said one of its planes bound for Christchurch on Thursday had to divert to Auckland to evade the ash.

Despite the diversion, Singapore Airlines said "all our flights to and from New Zealand and Australia are operating", but added that it was "closely monitoring the movement of ash clouds" in the two Pacific nations.

Air New Zealand said the cloud was now as low as 10,000 feet (3,000 metres) across parts of the South Island.

"Ash at these low levels gives us no choice but to cancel some services," chief pilot David Morgan said.

The widespread travel havoc followed the June 4 eruption of the Puyehue volcano, which had lain dormant for half a century.

Thick ash has been billowing out of the volcano and travelling across the southern hemisphere, recalling the widespread chaos in 2010 when an Icelandic volcano's eruption paralysed air traffic over Europe.

burs/jit