Jakarta Airport [CGK]

How the closure unfolded

Why ash closes an airport 150 km away

The instinct is to ask how a volcano that far away can ground flights in Jakarta. The answer is that distance is almost beside the point — wind direction is what matters. Anak Krakatau threw ash high into the atmosphere, and the prevailing winds carried it east, directly over the Jakarta metropolitan area.

Volcanic ash is not soft like wood ash. It is pulverised rock and volcanic glass, hard and abrasive, and it melts at temperatures below those inside a running jet engine. Fly through a cloud of it and the glass re-solidifies on turbine blades, chokes the airflow and can shut the engine down in flight. It also sandblasts windscreens and blocks the sensors that feed an aircraft’s airspeed instruments. There is no safe way to fly through it and no radar that reliably sees it, which is why the standard response is simply to stop.

That is also why reopening took longer than the ash took to clear. Before CGK could resume, air corridors had to be re-surveyed, ground crews had to sweep residual ash off runways and taxiways, and the 178 aircraft parked at the airport during the shutdown each had to be inspected for contamination in engines and sensors.

The scale of the disruption

• 8 airports closed, including Soekarno-Hatta and Halim Perdanakusuma in Jakarta.
• ~2,900 flights cancelled, delayed or diverted — more than 900 of them at CGK alone.
• 340,000+ passengers affected, with over 270,000 stranded at the peak of the disruption.
• Ash plumes to ~15,000 m (about 50,000 ft) on the Sumatra side, and roughly 6,000 m over Java.
• Two days of closure at CGK, from Sunday morning to just after midnight on Tuesday.

Those totals should be read as approximations, because the official counts do not match each other. Indonesian authorities were citing “more than 2,300 flights” and around 270,000 passengers for the period up to reopening. The Transport Ministry later settled on 2,961 flights and about 341,000 passengers across the eight airports. InJourney Airports, counting 5–8 September across its own network, puts it higher still at 4,174 flights and 455,754 passengers. The gap is probably a matter of what counts as “affected” and over which dates — a knock-on delay two days later is a judgement call — but nobody has published a reconciled figure, so treat any single number with caution.

Four of the eight closed airports are InJourney’s: Soekarno-Hatta, Halim Perdanakusuma, Husein Sastranegara in Bandung and Raden Inten II in Lampung. “The safety and security of passengers remains the priority in every operational decision,” InJourney chief executive Maya Watono said after the network reopened.

The response leaned on the rest of the network. Transportation Minister Dudy Purwagandhi designated Semarang and Surabaya as alternative landing points, with six airports across East Java, Central Java and Yogyakarta prepared to absorb diverted traffic. Free buses ferried passengers between cities, and immigration waived overstay penalties for foreign visitors whose flights had been cancelled. “We understand that this situation affects passengers’ travel plans,” airport spokesman Yudhistiawan said during the closure. “From the start of the temporary closure, we have focused on ensuring that passengers’ needs continue to be met.”

Where the flights actually went

When CGK shut, the inbound aircraft still had to land somewhere. Transportation Minister Dudy Purwagandhi named five alternative airports, all instructed to operate 24 hours for the duration. If you were on a CGK-bound flight that week, this is where you most likely ended up.

The lists do not agree at the edges. The ministry’s own briefings named those five; a detikcom photo report counted six, adding Adisutjipto in Yogyakarta; and InJourney Airports’ account of the week also mentions Bali’s I Gusti Ngurah Rai taking traffic. The five above are the ones every source agrees on.

“We encourage the use of alternative airports so that we can distribute passengers coming home, and they do not have to stay long in their departure countries,” Dudy said at Soekarno-Hatta on Monday 7 September.

Getting from a diversion airport back to Jakarta

Landing in Solo when you had booked Jakarta is only half a problem solved. InJourney Airports and the airlines put on free buses and trains linking Jakarta with Yogyakarta, Solo, Semarang and Surabaya. The first buses pulled out of Soekarno-Hatta at 21:00 WIB on Sunday 6 September, a little under twenty hours after the airport closed.

Passengers registered at posts set up inside Terminals 1, 2 and 3 — the verification desk at Terminal 1C handled much of the traffic. The same Service Recovery Activation covered food, drinks and set-aside rest areas in the terminals for passengers waiting it out.

One gap worth noting: Kertajati, which took Garuda’s long-haul arrivals, does not appear in the published lists of free bus and train destinations. We have not seen an official explanation, and passengers landing there may have been handled by their airline directly. If a future closure sends you to an airport outside that four-city list, ask your airline about onward transfer rather than assuming it is arranged.

None of this is a standing service. It was assembled for that specific closure, and a future one would need the same decision taken again.

Your ticket: a full refund, not compensation

These two get confused, and the difference matters. Volcanic ash is an extraordinary circumstance beyond the airline’s control, so statutory delay compensation does not apply. A refund is a different thing entirely, and it does.

On Monday 7 September the Transport Ministry instructed every airline to give passengers whose flights were cancelled a straight choice: a 100% refund, or rebooking onto another service. “The government ensures that passengers who choose to cancel their flight are entitled to a one-hundred-per-cent refund,” Dudy Purwagandhi said. The instruction was issued through the Directorate General of Civil Aviation under Lukman F. Laisa.

The practical lesson for next time: if a closure cancels your flight, you are not choosing between waiting and losing your money. Go to the airline — app or call centre, not the airport desk — and ask for the refund or the rebooking explicitly.

What a re-route actually means for your flight

Speaking at AirNav Indonesia’s office in Tangerang on Friday 11 September 2026, Capt. Nurcahyo Utomo, the agency’s Director of Safety, Security and Standardisation, said air traffic control is watching the volcano around the clock alongside the volcanology agency (PVMBG) and the meteorology agency (BMKG) — tracking not just the eruptions themselves but wind direction and where ash is likely to travel.

If ash threatens a corridor, the standard response is a re-route, and that word sounds more dramatic than it is. It means nudging aircraft around the affected block of airspace, not sending them somewhere else entirely. The example Nurcahyo gave: a Jakarta–Palembang service shifted slightly north of its usual track near Tanjung Karang. On a domestic sector that is a difference measured in minutes.

As of that Friday, AirNav said no domestic route was being re-routed, because the wind was carrying ash away from Soekarno-Hatta. The greater exposure, according to the agency, sits with international traffic crossing the region — the long-haul corridors between Australia and the Middle East pass close to the Sunda Strait, and those are the flights that would take the longer deviations.

The timing matters more than the distance. AirNav refreshes aeronautical information on a six-hour cycle as standard, and can issue an update within an hour if conditions change materially. That is why a NOTAM can appear with very little notice: during the closure itself, AirNav issued NOTAMs A3341/26, A3342/26 and A3344/26 within a few hours of each other on 6 September, coordinated through its Indonesia Network Management Center (INMC).

Capacity is the other constraint. CGK is worked at up to 81 movements an hour, and when it reopened the first wave was deliberately weighted toward departures — 61 out against 20 in — because the parking stands were full of the aircraft that had sat out the shutdown. A backlog at CGK clears by emptying the apron first, which is worth knowing if you are the inbound passenger waiting for that aircraft.

The practical upshot: a re-route is not a cancellation, and it is not something you need to act on. What it does tell you is that the decision cycle is short. If you are flying in the next few weeks, check your flight status close to departure rather than the night before.

Safe to fly is not the same as safe to breathe

The test that decides whether aircraft can operate is the paper test — sheets left out to catch ash particles. Those came back negative at Soekarno-Hatta, Halim, Husein Sastranegara and Budiarto before the airports reopened. Air quality for people on the ground is a separate question, and it did not clear as quickly.

Health Ministry monitoring on 8–9 September, released on 11 September, found PM2.5 of 63 µg/m³ at the DAMRI bus terminal at Soekarno-Hatta, against a safe threshold of 25 µg/m³. Several other outdoor points at and around the airport were also above the limit for PM2.5 and PM10. “The airport authority uses paper tests for flight safety, but it turns out particulate matter for health is still high,” Deputy Health Minister Dante Saksono Harbuwono said.

The readings that exceeded the limit were outdoors, which is where you are exposed at CGK: the kerbside drop-off, the bus bays, the open car parks and the walk between terminals. The ministry’s advice is to wear a mask for outdoor time in affected areas — sensible if you have asthma or another respiratory condition, are pregnant, or are travelling with young children or elderly relatives. We have not seen updated readings published since; if you are sensitive to air quality, treat the outdoor areas as the risk and do not assume the numbers have come down.

Where things stand now

CGK has been running a normal schedule since 8 September. The volcano, however, has not gone quiet. Anak Krakatau sits at Alert Level III (Siaga), the second-highest of Indonesia’s four levels, and the volcanology agency maintains a 3 km exclusion zone around the crater while warning that the probability of further eruptions remains high. The continuous eruption has settled back into intermittent Strombolian activity — occasional spurts rather than a sustained column.

Badan Geologi’s evaluation to 06:00 WIB on Friday 11 September recorded 14 Strombolian eruptions since the continuous phase ended at 00:04 WIB on 6 September, after 25 hours that began at 23:07 WIB on 4 September. The trend is downward and the alert level was still III on Saturday 12 September, but the agency has not lowered it, and magma supply is still being detected. In plain terms: the eruption that closed the airport is over; the eruption sequence is not.

For travellers that means the risk is real but not constant. A future closure would need a fresh eruption and winds pointing at Jakarta at the same time. Neither is forecastable weeks ahead, which is an argument for flexibility rather than for changing your plans.

If ash disrupts your CGK flight

• Check before you leave for the airport. During a closure the terminal is the worst place to be. The live departures and arrivals boards update faster than most airline notification emails.
• Contact your airline directly. Rebooking queues at the airport were hours long; app and call-centre channels moved faster. Airlines offered free rebooking and refunds throughout this closure.
• Ask for the refund by name. Statutory delay compensation does not apply to volcanic ash, but a refund does — the Transport Ministry ordered 100% refunds or free rebooking for cancelled flights during this closure. Do not accept a voucher if you wanted the money back.
• Consider the overland option. When Jakarta closed, flights kept running from Kertajati, Semarang, Solo, Surabaya and Yogyakarta, and free buses and trains linked four of those cities to Jakarta. For domestic trips, a train or bus to a working airport can beat waiting out a closure.
• Book insurance that names natural disasters. Many basic policies exclude volcanic disruption specifically. Check the wording rather than assuming.
• If you are already overseas and stranded, ask about overstay relief. Indonesian immigration granted it during this event; it is not automatic, but it is routinely offered when closures are officially declared.