Darwin remains cut off to all air services until Sunday, and flights from Australia to Bali are now affected, as three separate ash plumes billow from an Indonesian volcano.
The Sangeang Api volcano off the Indonesian island of Sumbawa is now erupting continuously after an initial blast on Friday afternoon, the Bureau of Meteorology's Volcanic Ash Advisory Centre in Darwin said on Friday.
Darwin International Airport was closed to all inbound and outbound flights on Saturday, while Bali's airspace is now also affected.
The major plume affecting Australian aviation is sweeping southeast over the west side of the Northern Territory as far south as Alice Springs.
The plume that is affecting Darwin would be around for the next 18 hours to 24 hours, said Volcanic Ash Advisory Centre assistant manager Cyndee Seals.
"It is starting to pull more westerly and it may move a little bit more to the north," she told AAP.
"We can see it right down to the Kimberley."
A second plume, hovering north of Darwin between 9.5km and 16km in the air, may cause problems for flights between Australia and Malaysia and Singapore..
A third, lower-level plume is drifting west from the volcano and is within 100km of Bali.
"The volcano is still erupting as it has done for most of the day, but not as violently as initially erupted but there is a steady plume," VAAC spokesman Tim Birch said.
Virgin Australia spokeswoman Jacqui Abbott confirmed two Saturday afternoon flights to Denpasar - one from Adelaide and on from Melbourne - have now been cancelled.
Qantas Group spokeswoman Kira Reed said Jetstar has cancelled an Adelaide-Denpasar flight that went via Darwin, and all its services to and from Darwin remain grounded.
Earlier, Deputy Prime Minister Warren Truss said it may be days before flights through northern Australia return to normal.
"Depending on wind and other weather conditions, the ash has the potential to affect flights to and from other airports, including Brisbane, during coming days. This is currently being fully assessed," he said.
"Passengers are advised to check with their airlines for further information."
Airservices Australia has begun diverting international flights around the ash cloud.
The Civil Aviation Safety Authority says volcanic ash can affect all aircraft with piston or jet engines at all flight levels.
Fine particles of pulverised rock consisting mainly of silica contained in volcanic ash clouds can be highly abrasive and damage aircraft engines, structures and windows.