Widespread Haze from Indonesian Forest and Peatland Fires Disrupts Flights Across Kalimantan

Large-scale forest and peatland fires in Kalimantan and Sumatra, Indonesia, have triggered widespread haze. Smoke is drifting downwind from fire hotspots, affecting not only Indonesia but also neighboring countries including Malaysia, Brunei, Singapore, and the Philippines.Particularly in Kalimantan, severely reduced visibility caused by haze has disrupted flight operations, leading to cancellations, delays, and revised arrival and departure times at several airports.

Moderate to Severe Transboundary Haze Spreads Across the Region

Moderate to severe haze has spread across Kalimantan, Sumatra, western Peninsular Malaysia, and Sarawak, crossing borders into surrounding regions.

According to ASEAN weather and haze bulletins as of 11:00 AM on September 17, scattered showers were observed across parts of Peninsular Malaysia, northern Kalimantan, and northern Sumatra. In contrast, dry conditions have persisted across much of the southern ASEAN region, especially overnight.

Air quality monitoring stations across Sumatra and Kalimantan have registered Air Quality Index (AQI) readings ranging from "Unhealthy" to "Hazardous." Several stations in western Peninsular Malaysia and Sarawak have also recorded "Unhealthy" levels of air pollution.

Extremely High PM2.5 Concentrations Raise Health Concerns

According to the Indonesian Ministry of Health, more than 12.5 million people across seven provinces, including those in Kalimantan and Sumatra, have experienced adverse health effects associated with the haze.【1】

According to observations from PurpleAir, daily average PM2.5 concentrations at some monitoring sites in Kalimantan have exceeded 150 µg/m³ since late August. Some locations have recently recorded daily average concentrations above 400 µg/m³, indicating extremely high levels of air pollution.【2】

These concentrations are far above the World Health Organization (WHO) 24-hour guideline of 15 µg/m³【3】 and Japan's environmental standard of 35 µg/m³ for daily average concentrations【4】, raising concerns about potential adverse health effects on local populations.

Flights Disrupted in Pontianak and Surrounding Hubs

In Pontianak, the provincial capital of West Kalimantan, haze from wildfires has disrupted flight operations at Supadio International Airport (WIOO/PNK). Supadio International Airport serves as the primary international gateway for West Kalimantan, functioning as a vital air transport hub linking Pontianak with major Indonesian cities such as Jakarta and Surabaya.

Ongoing haze from recent forest and peatland fires has led to continuous degradation in visibility at the airport. METAR observations over the past week have repeatedly reported visibility dropping below 4,000 meters, occasionally falling below 800 meters. Fog (FG) and haze (HZ) have also been frequently logged.

Visibility deteriorated sharply on September 15, dropping to a low of 200 meters with vertical visibility reported at 200 feet (VV002). On September 16, severely degraded visibility persisted between 300 and 600 meters, continuing to impact aircraft takeoffs and landings.

Depending on smoke density and shifts in wind speed and direction, airport visibility could deteriorate rapidly within short timeframes. The resulting air transport disruptions threaten not only commercial passenger services but also air freight operations, regional logistics, and broader economic activity.

Ongoing Risk of Persistent Haze in Arid Zones

Over the coming days, scattered showers are forecast across Peninsular Malaysia, northern and central Sumatra, and northern Kalimantan. In areas receiving rain, hotspots and haze levels may see temporary relief. However, dry conditions are projected to persist across extensive swathes of southern ASEAN. In regions where dryness continues—such as Kalimantan and central-to-southern Sumatra—hotspots and haze are expected to remain elevated, with the risk of evolving into severe transboundary haze events. Prevailing southeasterly to southwesterly winds across southern ASEAN are likely to transport smoke across broad downwind areas, potentially prolonging impacts in Malaysia, Brunei, Singapore, and parts of the Philippines.

Flight Disruptions Likely to Extend Through October

In areas subject to prolonged dry spells, haze conditions may persist through October. Airports across Kalimantan and Sumatra are expected to face ongoing operational challenges, with flight schedules subject to disruption from reduced visibility and procedural operational adjustments.

SkyAviators, the aviation decision-support tool for airline operators.  Learn more about "SkyAviators"

Sources

【1】 IQAir, Wildfire Map Spotlight: Indonesia Forest and Peatland Fires, September 2026

【2】 PurpleAir, PurpleAir Map – PM2.5

【3】 World Health Organization (WHO), WHO global air quality guidelines

【4】 Ministry of the Environment, Japan, Environmental Quality Standards for Air Pollution