There has been no slump in tourism to Bali — despite the threat of an eruption that could close the airport for an extended period of time.
Passenger numbers are stable at around 50,000 to 60,000 visitors per day, Ngurah Rai International Airport communications chief Arie Ahsannurrohim said.
"As long as the volcanic ashes don't have any impact on Bali's airport, it will not be closed," he said.
"If there are volcanic ashes — it will be closed."
About 400 planes come in and out of Bali each day, including about 50 from Australia.
Mr Ahsannurrohim said in the case of an eruption, the planes in the air would be diverted to seven regional airports, including Solo and Surabaya on the island of Java.
Departing passengers would be given help to get transport to the alternative airports, he said.
"If there is volcanic ash, first we will activate the disaster response command post in the airport, then we'll help the airlines with a helpdesk, so passengers will be able to get updates of their flight status," Mr Ahsannurrohim said.
"Then we'll provide different options of transport to passengers who cannot fly."
In the case of eruption, ground handling crews in Bali would work quickly to protect planes from any ash, he said.
The fine particles can cause severe damage inside engines.
Threat 'doesn't mean it will definitely erupt'
Bali has been declared a natural disaster zone, with about 50,000 people now living in emergency accommodation outside a 12-kilometre Mount Agung exclusion zone.
Bali authorities said 64,000 people lived inside the zone before Agung began rumbling.
Around 1,000 tremors a day are being recorded on the mountain, and vulcanologists said that suggested an eruption was imminent.
Indonesia's National Disaster Management Agency chief Sutopo Purwo Nugroho said volcanoes were an unpredictable business.
"Mount Agung is now in a critical phase, which means all the instrument observations show that magma is pushing up towards the surface but the rock 'plug' has stopped it from coming out," he said.
"So even though a level four alert has been declared, it doesn't mean it will definitely erupt.
"It depends on the energy that pushes the magma. We can't give you an estimation of when exactly it will erupt."
Indonesian President Joko Widodo is due in Bali today to see the scale of the crisis for himself.