An eruption of Indonesia’s Mount Anak Krakatau suspended operations at Jakarta’s main international airport on Sunday, disrupting 209 flights including several international services.

Soekarno-Hatta International Airport announced on Instagram that it had halted flight operations until 9.30 a.m. local time (0230 GMT) because of volcanic ash, extending a stoppage originally due to end at 5.30 a.m. Indonesia’s transport ministry gave the number of affected flights.

The volcano has been erupting since late on Friday, with ash detected over the airport early on Sunday.

Ash to 50,000 feet

The meteorological agency BMKG said ash reached 20,000 feet (6,000 metres) on the Java side of the volcano and a plume of up to 50,000 feet (15,000 metres) on the Sumatra side, extending over parts of Banten province in Java.

Schools cancelled activities on Saturday, with students and residents reporting eye irritation from falling ash, and fishing crews stayed in port, the Indonesian outlet Kompas reported.

The disaster mitigation agency BNPB urged residents to stay calm but vigilant.

“In the event of ashfall, people are advised to wear masks and eye protection, reduce outdoor activities, cover water sources and exercise caution when driving, as volcanic ash can reduce visibility,” spokesperson Berton Panjaitan said.

BNPB said on Saturday there was no imminent tsunami risk.

Why that assurance matters

Anak Krakatau — “Child of Krakatoa” — sits roughly midway between Java and Sumatra on the Pacific “Ring of Fire.” In December 2018, a flank collapse during an eruption sent a tsunami into coastlines on both islands without warning, killing hundreds and injuring hundreds more. The volcano emerged from the caldera left by the catastrophic 1883 Krakatoa eruption.

Soekarno-Hatta is also a connecting point for Sri Lankan travellers routing through Southeast Asia.

Correction: this article originally stated that Sri Lanka has no direct flights to Jakarta. SriLankan Airlines operates a direct Colombo–Jakarta service, UL364/UL365, both legs of which were cancelled on 7 September — see the update below.

Update: two SriLankan Airlines flights rerouted

The disruption reached Sri Lankan operations later on Sunday. Two SriLankan Airlines flights due to arrive from Sydney and Melbourne that night were being rerouted, Ada Derana reported. Several Middle Eastern carriers flying between Australia and Indonesia were also diverted.

Indonesian aviation authorities issued a notice restricting aircraft from a large section of airspace west of the volcano — including airspace south of Sri Lanka — because ash and rock particles containing silica had spread across a wide area of the upper atmosphere, posing a risk to aircraft engines and control systems.

That is what put the Australia–Sri Lanka routings inside the affected zone: the closure is not confined to Indonesian airspace, and the flights concerned do not serve Jakarta at all.

Update: 150,000 stranded, and the flight count more than doubles

More than 150,000 passengers were left stranded after Indonesia suspended operations at six airports, the Daily Mirror reported.

Transport Minister Dudy Purwagandhi put the number of flights affected at 467 — more than double the 209 the ministry gave earlier in the day — and asked airlines to consider diverting to other airports. The decision to close further airports followed tests showing ash had spread towards West Java.

Soekarno-Hatta was the first to close on Sunday morning. The pause mainly hit flights to and from Singapore, along with Doha, Sydney and Kuala Lumpur routes. Two further eruptions occurred early on Sunday, after continuous seismic activity, lava fountains and booming sounds since Friday night.

Purwagandhi urged airlines to speed up ticket refunds and to keep passengers informed to avoid overcrowding at airports. The health minister asked residents in affected areas to stay indoors and wear masks against respiratory, eye and skin risks.

Authorities again confirmed no tsunami warning is attached to the current activity.

Update, September 7: SriLankan cancels both Colombo–Jakarta legs

SriLankan Airlines cancelled Monday’s scheduled services in both directions between Colombo and Jakarta — UL364 (Colombo–Jakarta) and UL365 (Jakarta–Colombo), Ada Derana reported. NewsFirst, reporting the inbound cancellation, said that flight had been due into Katunayake at 5.30 p.m. Sri Lanka time.

The airline said Indonesian authorities have restricted flights through the affected western air corridor towards Sri Lanka. The cancellations follow Sunday night’s diversion of the Sydney and Melbourne services.

Update, September 7: eight airports shut, no end date

Eight Indonesian airports, including two serving Jakarta, remained closed early on Monday, Ada Derana reported, citing the transport minister. They include airports serving the neighbouring provinces of Lampung and West Java.

“We cannot ascertain when this will end due to the dynamic weather,” Transport Minister Dudy Purwagandhi said.

The airports were to stay shut until at least 8.59 a.m. local time, after which Soekarno-Hatta said on Instagram that operations would remain suspended until 6 p.m. local time. Singapore Airlines cancelled 18 flights on Monday and a further departure early on Tuesday.

The transport ministry put the number of people affected by flight cancellations at 170,000 — a figure NewsFirst also carried. That is only about 13% above the 150,000 the same ministry gave on Sunday, even though the number of closed airports rose from six to eight over the same period. The two figures may not be measuring the same thing: Sunday’s was reported as passengers stranded, Monday’s as passengers affected by cancellations.

The most recent eruption was at 8.23 p.m. on Sunday. Ash has reached 6,000 m on the Java side and 15,000 m on the Sumatra side, BMKG said. Schools in Jakarta and Lampung have moved to remote learning.

Update, September 7 evening: 340,000 stranded, reopening pushed to midnight

The stranded figure doubled over the course of Monday. More than 340,000 passengers are now stranded across Indonesia after the eruption disrupted nearly 3,000 flights, with airports suspending operations for a second day, Ada Derana reported, carrying BBC copy.

Soekarno-Hatta decided not to reopen at 6 p.m. local time (11.00 GMT) as it had earlier said it would, because volcanic ash was still present near its airspace. Flights are now set to resume at 11.59 p.m. on Monday. Halim Perdanakusuma, the smaller airport serving civil and military flights, stays closed until the same time.

Note the framing has shifted again. The transport ministry’s Monday morning figure was 170,000 affected by flight cancellations; this later figure is 340,000 stranded — exactly double, and once more not plainly the same measure. The flight count has moved further still, from 209 on Sunday morning to 467 on Sunday evening to nearly 3,000 by Monday evening. No outlet reconciles the three.

At the airport

Queues formed in the departure halls at Soekarno-Hatta on Monday as passengers sought refunds and news of when they could fly.

Finna, 46, who had been due to fly home to Jakarta from Malang in East Java on Sunday morning, described repeated rescheduling. “It was very crowded because passengers from the morning flights had piled up, while those scheduled for later departures still didn’t know what would happen,” she told BBC Indonesian. “We were all glued to the flight information screens.” She gave up and spent the night on two intercity trains, reaching Jakarta at 3 a.m. on Monday.

A newly married Malaysian couple who had spent a week in Bali were told the next flight to Kuala Lumpur would not leave until September 11. “What are we going to do here for another five days? We only prepared enough money for our honeymoon,” Amir Hamzah, 29, told the Malaysian news agency Bernama.

Jo Shaw, visiting with the conservation charity Save the Rhino International, said her team had abandoned plans to camp at Java’s Ujung Kulon National Park after the alert level was raised. “Being stranded in an airport hotel is a relatively minor inconvenience,” she said, adding that she was more concerned for the teams working with rhinos in the conditions.

The volcano

Indonesia’s Geological Agency warned on Monday that “the probability of further eruptions in the coming periods remains high.” Authorities have barred activity within a 3 km radius of the active crater, and ships passing through the Sunda Strait are prohibited from an exclusion zone of the same radius. Transport Minister Dudy Purwagandhi said airports were running ash-spread tests every 30 minutes.

Authorities again confirmed there is no tsunami warning attached to the current activity.

Sources