Speaking to the press, Santoso explained that the raising of the alert warning level to its maximum level of “4” has yet to have any impact on domestic and international flight operations to and from Bali. At the same time, the Directorate and all related stakeholders already have contingency plans in place to address the impact of any eruption on normal flight activities.

Until Saturday morning, September 23, 2017, there was no detection of volcanic ash emitted from Mount Agung and all flight operations to and from Bali were operating normally.

Accordingly, Virgin Australia announced on Saturday, September 23, 2017, that all flights heading to Bali were stopping in Darwin to take on additional fuel that would allow them to return to Australia if Mt. Agung erupted while their flight was on a final inbound sector to Bali.

"Seventy to 80 per cent within days, probably 90 per cent within weeks to months, but I'm reserving that 10 per cent in case it doesn't happen — so the odds are on, but whether it proceeds to an eruption or not is still uncertain," he said.

When volcano experts say Bali's Mount Agung is "extremely likely" to erupt within hours or days, it is because of charts like the one above.
Stations routinely collect data on tremors within the mountain, with a spiky red line charting the rise and fall of Agung's mood day after day.