Anak Krakatau's strongest eruption of 2026 sends ash toward Jakarta — Soekarno-Hatta airport closed overnight, 33 flights disrupted

Safety & SecurityIssued: September 6, 2026日本語版はこちら →

Mount Anak Krakatau in the Sunda Strait, on Level III (Siaga) alert since 2 July 2026, entered a continuous lava-fountain eruption on the night of Friday 4 September 2026 — the most intense of the year, with satellite-detected ash reaching roughly 14–15 km. BMKG's dispersion data as of 04:00 WIB on Sunday 6 September showed the low-level ash cluster spreading over parts of Jakarta, Banten and West Java, with confirmed ashfall on the Serang coast. After paper tests detected ash at the airport, Soekarno-Hatta (CGK) was closed under NOTAM A3341/26 from 01:30 WIB on 6 September; 33 flights had already been cancelled, delayed or diverted by the previous evening. Volcanologists have stated the rebuilt cone is too small to trigger a tsunami.

Key points

Alert level: Level III (Siaga) since 2 July 2026; more than 240 eruptions recorded since then. Badan Geologi / PVMBG maintains a 3 km exclusion radius around the crater for residents, visitors and climbers.
The continuous eruption began around 23:07 WIB on the night of 4 September 2026 (PVMBG's release is dated 5 September) with audible rumbling; seismic duration reached 21,600 seconds at 70 mm amplitude — the strongest activity of 2026. PVMBG could not observe the column visually, but satellite data (including Japan's Himawari-9) put the ash at roughly 14–15 km (48,000–50,000 ft).
PVMBG explicitly stated the cone rebuilt since the December 2018 collapse is still relatively small and does not have the potential for a collapse that could trigger a tsunami, and asked the public not to be swayed by tsunami rumours.
BMKG (06:00 WIB, 6 September): two ash clusters — the surface-to-20,000 ft cluster spreading northeast-to-south over parts of DKI Jakarta, Banten and West Java (detected as far as Bandung); a second cluster over Lampung, Bengkulu and the southern Sunda Strait.
Confirmed ashfall on the ground in coastal Serang regency, Banten, where residents reported stinging eyes and sore throats and some schooling was disrupted; BPBD units in Banten and Lampung advised masks outdoors, reduced outdoor activity and extra care when driving because of reduced visibility.
Soekarno-Hatta (CGK, Tangerang): paper tests at 00:35–01:05 WIB on 6 September were positive for volcanic ash, and the airport was closed under NOTAM A3341/26 from 01:30 WIB. The Ministry of Transport said the closure was scheduled to 05:30 WIB and that operations resumed normally with no further ash detected; at least one outlet reported the closure running to 09:30 WIB — confirm your flight status directly with the airline.
Flight impact as of 22:00 WIB on 5 September: 33 flights affected at CGK — international 16 cancelled, 7 delayed, 5 rescheduled; domestic 4 cancelled and 1 diverted, on routes including Lampung (TKG), Denpasar (DPS) and Surabaya (SUB). The Directorate General of Civil Aviation is coordinating with airlines, the airport operator, AirNav Indonesia and BMKG, with decisions taken dynamically.
As of writing, no 2026 advisory specific to this eruption was located on the Japanese Embassy in Jakarta's notice page; check the Embassy's site directly for the latest guidance.

What this means for your Indonesian entity

For your Indonesian entity this is an operations and travel issue, not a compliance one. Three practical checks: (1) Travel — anyone flying in or out of Soekarno-Hatta in the coming days should confirm status with the airline before leaving for the airport and build in slack; closures are being decided from live paper tests, so they can recur at short notice while the eruption continues. (2) Staff — if your office or your employees' commutes are in Tangerang, western Jakarta or coastal Banten, follow BPBD guidance: masks outdoors, limit unnecessary outdoor work, and allow extra time on the road given reduced visibility. (3) Rumours — PVMBG has ruled out a tsunami-scale collapse; treat viral tsunami warnings as unverified unless they come from BMKG or Badan Geologi. Regulatory filings and deadlines are unaffected. For street-level and evacuation guidance the Japanese Embassy's advisories are authoritative; we track the situation but are not a substitute for them.

Sources

This page summarises publicly available information for orientation. It is not tax, legal, or accounting advice, and regulations change. Verify against the linked primary sources and contact us before acting on anything here.

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