Mount Anak Krakatau, about 850km south-south-east of Singapore, began erupting late on Sept 4, disrupting flights and daily life as volcanic ash spread more than 150km away, blanketing Jakarta and nearby areas.

As at Sept 7, seven Indonesian airports remain shut due to volcanic ash.

A map of eastern China highlighting the Grand Canal, running from Beijing to Shanghai, with labels showing major cities and notes on China’s extensive inland waterways.

Sulphur dioxide data is from an analysis by the Copernicus Atmosphere Monitoring Service (CAMS), valid at 8pm SGT on Sept 6.

Seven Indonesian airports, including two serving Jakarta, remained closed on Sept 7 because of volcanic ash from the eruption at Mount Anak Krakatau, according to the Transport Ministry.

Ash from Anak Krakatau, which sits halfway between Java and Sumatra islands, has blanketed Jakarta and several surrounding areas since it erupted late on Sept 4, leading to the closure of the airports for safety reasons.

More than 270,000 people have been affected by the delay, diversion or cancellation of 2,300 flights, according to the ministry.

A map showing air traffic around Anak Krakatau cleared due to cancelled flights and airport closures.

Source: Open Sky. Data collected on Sept 7, 4.41pm.

A Changi Airport Group spokesman said 31 flights between Singapore and Jakarta scheduled for Sept 7 had been cancelled as at 7pm, with additional staff deployed to assist affected travellers and manage queues.

Singapore Airlines (SIA) cancelled nine flights from Singapore to Jakarta and nine in the opposite direction on Sept 7. The airline also cancelled its 5.25am Jakarta-Singapore service on Sept 8.

SIA is putting on additional services between Singapore and Surabaya to provide passengers with another way to travel between the two countries.

Two additional Singapore-Surabaya flights are scheduled to depart at 9.40pm on Sept 7 and 12.40am on Sept 8, with two additional return services from Surabaya in the early hours of Sept 8.

Passengers affected by the Jakarta cancellations can also rebook on other SIA services between Singapore and Indonesia, the airline said.

Scoot, meanwhile, cancelled five Singapore-Jakarta and five Jakarta-Singapore services on Sept 7. Affected passengers can rebook alternative Scoot flights to or from other Indonesian destinations, or request a full refund.

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An aerial view shows steam and volcanic ash billowing from Mount Anak Krakatau in the Sunda Strait, Indonesia. PHOTO: Indonesia's Center for Volcanology and Geological Hazard Mitigation via AFP

Indonesian Transport Minister Dudy Purwagandhi said the decision to keep the seven airports closed was based on the latest data from Indonesia’s meteorological agency, BMKG.

Tests for volcanic ash were being conducted every 30 minutes as the authorities continued to monitor conditions.

Changing wind directions at different altitudes meant ash was continuing to linger around airports near Anak Krakatau, making it difficult to predict when they could safely reopen, Dudy said.

“We cannot determine or ensure whether an airport is safe from the spread of ash,” he told reporters, adding that tests were also being conducted at other airports around the affected area.

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A man clearing volcanic ash from his car following the eruption of Mount Anak Krakatau. PHOTO: AFP
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A woman sweeping a floor covered with volcanic ash at Pasauran village, following the Mount Anak Krakatau volcano eruption. PHOTO: Reuters
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Firefighters spraying water to clear volcanic ash following the Mount Anak Krakatau volcano eruption. PHOTO: Reuters

Anak Krakatau is one of about 130 active volcanoes in Indonesia, which straddles the Pacific Ring of Fire, a highly seismically active zone where different plates on the earth’s crust meet to create a large number of earthquakes and volcanic eruptions.

Anak Krakatau, which means child of Krakatau, began emerging a century ago from the area previously occupied by Krakatau, then known as Krakatoa.

The older volcano destroyed itself in mass eruptions in 1883, which killed more than 36,000 people after triggering a series of tsunamis.

A tsunami after an eruption at Anak Krakatau in 2018 killed over 400 people.