November 20, 2025 | 04:11 pm
TEMPO.CO, Jakarta - Airnav Indonesia announced that the activities of several flight routes remained relatively normal following the eruption of Mount Semeru in Lumajang Regency, East Java, until Thursday, November 20, 2025. "Until the notice is released, the situation has yet to necessitate the closure of airspace due to the threat of volcanic ash cloud," said EVP of Corporate Secretary AirNav Indonesia Hermana Soegijantoro.
This situation, said Hermana, also applies to airports around East Java, such as Malang, Banyuwangi, Surabaya, and Yogyakarta. "Everything is still operating as normal. No airports have been closed, and so far, no flights have been canceled," he said.
However, Hermana emphasized that AirNav Indonesia continues to intensively monitor flight routes and airports that are potentially affected, and consistently inform the latest developments through the issuance of ASHTAM. "The latest update is ASHTAM number VAWR6038 which we released through the International NOTAM Office AirNav Indonesia on November 20, 2025, at 02:00 UTC (09:00 a.m. local time)," he said.
The report stated that Mount Semeru was designated as "Red Code," which means that the eruption activity is quite significant and has the potential to disrupt flight routes. Volcanic ash was observed at two different altitudes. At the lower level, the ash spread was at the surface up to about FL150 (4,500 meters), moving southeast at a wind speed of around 5 knots.
Then, at the higher level, the ash spread reaches about FL450 (13,500 meters), moving southwest at a speed of about 15 knots. "ASHTAM is a notification in a special language that we issue to inform about changes in volcanic activity, eruptions, and volcanic ash clouds that may affect flight operational activities," said Hermana.
Hermana stated that Airnav releases ASHTAM to all relevant parties, both domestically and internationally. ASHTAM, containing technical information, is an important reference for all aviation stakeholders in making decisions related to mitigation, adjusting flight routes, and air traffic management. This document is issued as a flight safety warning because Mount Semeru is still observed to emit volcanic ash.
Hermana explained that this information is collected by the NOTAM Office AirNav Indonesia from various sources, including Himawari-8 satellite images, monitoring cameras (webcams), and data from the Center for Volcanology and Geological Hazard Mitigation (PVMBG). In the last observation before ASHTAM was released, the volcanic ash at a high altitude was difficult to see due to weather clouds, but the movement model indicated that the ash would weaken in the next few hours.
Meanwhile, the ash at a low altitude was still clearly observed and continued to move southeast. "However, the current trend shows that the spread of volcanic ash is moving further away from the surrounding airports and potential flight routes that could be affected," he said
Today, Hermana continued, AirNav also collected data from the results of paper tests conducted by PT Angkasa Pura Indonesia and the Airport Authority Office (Otban) at nearby airports, such as Abdurrahman Saleh Airport (Malang), YIA and Adi Sucipto Airport (Yogyakarta), and Adi Sumarmo Airport (Solo). "Alhamdulillah, all the results were negative," she said.
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