Anak Krakatau eruption disrupts hundreds of flights as ash reaches 50,000 feet

Indonesia’s Anak Krakatau volcano has erupted, sending volcanic ash as high as 50,000 feet (15,000 metres) and causing major disruption to air traffic, including the temporary closure of Jakarta’s main international airport.

Jakarta Soekarno-Hatta International Airport (CGK) was temporarily closed on Sunday after volcanic ash was detected in the airport area. According to Indonesia’s Directorate General of Civil Aviation, 209 flight movements were affected, and 22,798 passengers were impacted during the closure period.

The disruption included 16 cancelled international flights, seven delayed flights and five rescheduled flights, involving destinations including Kuala Lumpur, Singapore, Hong Kong, Sydney, Seoul/Incheon, Doha and Amsterdam. Four domestic flights were also cancelled, and another was diverted.

Airlines including Singapore Airlines and Malaysia Airlines cancelled Jakarta services, while Qantas reported disruption to several flights. Other international routes affected included Singapore, Kuala Lumpur, Doha and Sydney.

Ash reaches airline cruising altitudes

The aviation concern is the altitude and extent of the ash plume.

The Darwin Volcanic Ash Advisory Centre (VAAC) reported continuous volcanic ash reaching FL500, or approximately 50,000 feet, with the high-level plume moving west at around 30 knots. Lower-level ash was reported up to FL200 (20,000 feet) and moving towards the south and southeast. The advisories were based on Himawari-9 satellite imagery and dispersion modelling.

Volcanic ash poses a serious hazard to aircraft because it can be ingested by jet engines, where it can melt and adhere to hot turbine components, potentially causing engine damage or loss of thrust. Ash can also damage windscreens, sensors and other aircraft systems.

The Indonesian authorities therefore suspended operations at several airports as the ash spread through western Indonesia. Alternatives including Kertajati, Ahmad Yani and Juanda airports were identified for possible diversions where operationally feasible.

The eruption began after increased volcanic activity from Anak Krakatau, which has been at alert level 3 since July 2. The volcano, located in the Sunda Strait between Java and Sumatra, has a particularly notorious history: its 2018 eruption triggered a tsunami that killed more than 400 people. No tsunami threat has been reported from the current eruption.

With further eruptions recorded on Sunday and volcanic ash continuing to be monitored, airlines and Indonesian aviation authorities are closely watching the movement of the ash cloud before restoring normal operations.