If history's anything to go by, the smoking volcano that's stranding hundreds of Australians in Bali may be wreaking havoc for some time.
The last time Mount Rinjani became active in 2009, it lasted 18 months.
Moated by a lake in the highlands of Lombok, the volcano has been spewing ash since last Wednesday, grounding almost all flights in and out of Denpasar, near Bali's resort strip.
The Bureau of Meteorology's Darwin Volcanic Ash Advisory Centre is monitoring the cloud and meteorologist Steph Bond told The Huffington Post Australia there was no telling when it would end.
Pretty though it is, Mount Rinjani is wreaking havoc on flights.
"There's no indication it will decrease in energy any time soon and the last time it was active in 2009, it went on for 18 months," Bond said.
"Sometimes they’ll increase in energy but sometimes they dissipate. Volcanoes are are highly unpredictable in their energy outputs.
"In a sense, it's up to fate."
Bond is part of an international team monitoring volcanic ash for the aviation industry.
She said the fine particles could take down a plane.
"Any type of ash is harmful to airplanes, because it's very abrasive to the fuselage but also if it gets into the engines, it can melt like glass and stop them working."
While flights are grounded, the team will watch the ash cloud waiting for safe conditions, but she said it was complicated.
Passengers line up after their flights were canceled at Bali's international airport, in Denpasar.
"The problem with the tropics is the level the ash rises to has winds that are very light and variable," Bond said.
"The wind direction can change six times in day, which makes it very hard to forecast."
Airliner Virgin Australia released a statement on Monday saying conditions remained unpredictable and all flights were grounded.
"Our priority is to bring guests home from Bali, rather than fly more guests in who could potentially be delayed in returning home due to ongoing eruptions," the statement said.
"Therefore Virgin Australia remains ready to send aircraft over to Bali as soon as we receive advice that conditions in the vicinity of Denpasar airport will be safe for flying."
Virgin is also offering those booked in to fly to Bali this week the option of travelling to Fiji, Vanuatu, Thailand and other options instead.
Jetstar also cancelled flights, saying: "We will only resume operating services to and from Bali once flying conditions around Denpasar Airport have improved. We make these assessments independent of the airport and other airlines."
Jetstar is offering upcoming customers the option of switching to Fiji, Thailand, Hawaii, New Zealand or other domestic locations free of charge.
Melbourne Airport at the strike's worst on Monday morning. Picture: Penny Stephens
In Australia meanwhile, despite warnings of airport chaos brought about by a 24-hour customs strike, Monday morning's rush hour passed relatively smoothly.
Passengers tweeted from Sydney, Melbourne and Hobart to report easy arrivals and departures, with one even suggesting the trip was so easy, customs should strike more often.
In Brisbane, however union staff reported two-hour delays.
The 24-hour strike is part of industrial action by 10,000 Border Force workers for better pay and conditions in the face of Federal Government changes that the Community and Public Sector Union said would result in $20,000 pay cuts for some workers.
Monday's strike action took place at all of Australia's eight international airports, maritime ports and mail centres.
CLARIFICATION: The headline of this story has been updated on advice to clarify the volcanic activity prompting flight delays could continue for 18 months.