Qantas and Jetstar cancelled flights to and within New Zealand on Monday as a cloud of ash from an erupting volcano in Chile drifted across the country.
Air New Zealand continued domestic flights, changing altitudes at which planes flew and altering flight paths to avoid the ash.
During the day, the Civil Aviation Authority raised the recommended altitude that planes could fly at from 20,000 to 27,000 feet, meaning there is greater space for planes to fly in.
CAA spokesperson Bill Sommers said the base of the cloud had risen to 27,000 feet on Monday afternoon, however there was no guarantee it would not descend again and the authority would continue to monitor the situation.
Both Qantas and Jetstar resumed flights in and out of Melbourne, where they said the ash had cleared, but neither specified when services in New Zealand would resume.
Pacific Blue cancelled six trans-Tasman flights and was monitoring the situation. Emirates has not cancelled any.
Disruption tipped for more than a week - CAA
The CAA says air travel could be disrupted for more than a week by ash from the Chilean volcano.
CAA meteorological manager Peter Lechner told Morning Report that as long as the volcano was erupting there will be issues with the airspace in New Zealand.
He said there will be disruption to air travel for possibly a week or more but whether there is a problem on a daily basis will depend on the ebb and flow of air masses over the country.
At the moment the ash is basically trapped in the stratosphere, it's not falling below that, so the air space below the ash cloud is viable for operations,'' he said.
The Puyehue Cordon Caulle volcano chain in Chile has been disrupting travel in Argentina, Uruguay and Brazil, since it began erupting on 4 June.
Jetstar's domestic terminal at Auckland airport was deserted on Monday morning. Many displaced passengers were joining the queue for Air New Zealand flights, a queue that was steadily getting longer.
A Radio New Zealand reporter said there was some frustration at the international terminal as travellers tried to figure out when they might be able to fly again.