A cloud of ash from an erupting volcano in Chile drifted higher over New Zealand and Australia on Monday, easing the threat to commercial aircraft, after scores of flights had been cancelled over the past two days, grounding thousands of people.
Australia's national carrier Qantas resumed flights in and out of the southern city of Melbourne, but was still not flying to or from New Zealand.
Flights between the two countries and some domestic routes in both had been affected by the cloud, which has travelled some 10,000 km (6,000 miles) across the Atlantic and Indian oceans, settling over their southern air space.
New Zealand's Civil Aviation Authority said the cloud had moved higher with the base at around 27,000 feet from the previous 20,000-foot level.
"That gives the airlines a bit more flexibility on operations, but it is completely their decision on whether they fly," spokesman Bill Sommer said.
Air New Zealand kept in the air by re-routing flights and flying at lower altitudes to avoid the ash, but was monitoring developments closely.
"We will not fly through ash and are constantly taking guidance from CAA... to ensure we can continue to carry passengers only where safe routes and altitudes are available," said Air NZ chief pilot David Morgan.
Air NZ flights had been operating at around 18,000 feet although it meant fuel consumption was up around 10 percent.
Virgin Australia, which had cancelled services on Sunday, resumed flights on Monday.
An estimated 60,000 passengers, mostly in Australia, had been affected, as around 200 flights were cancelled.
Despite the disruptions, airports in both countries reported little turmoil at terminals on Monday, with many affected passengers abandoning their travel plans for now.
The fine ash particles, 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.
DISRUPTION IN CHILE, ARGENTINA
The volcano in the Puyehue-Cordon Caulle chain in Chile has been erupting for the past week, throwing South American air travel into chaos as it spews ash high into the atmosphere.
In Argentina, where the ash has closed roads and blanketed Patagonian grazing pastures and a ski resort, state-run Aerolineas Argentinas said it had cancelled local and international flights again late on Sunday.
Chile's LAN halted services to and from Buenos Aires, saying it was "constantly monitoring the weather conditions."
Air travel in northern Europe and Britain was disrupted last month after Iceland's most active volcano at Grimsvotn sent a thick plume of ash and smoke as high as 25 km.
Last April, an eruption of another Icelandic volcano, Eyjafjallajokull, caused worldwide aviation chaos with 100,000 cancelled flights, affecting an estimated 10 million people at a cost of USD$1.7 billion.
This was worse than the Chile disruption because it spread ash throughout the air column, from ground level to the upper atmosphere.