Indonesia has closed eight airports and cancelled hundreds of flights as Anak Krakatau, located between Java and Sumatra, erupted violently, spreading ash across the country’s two most populous islands.

As of Sunday, 1,558 international and domestic flights were cancelled or delayed, affecting more than 170,000 passengers. Jakarta’s Soekarno-Hatta International Airport was shut on Sunday and into Monday morning. Transport minister Dudy Purwagandhi said the situation remained unpredictable due to dynamic weather conditions.

Authorities urged residents in Java and Sumatra to stay indoors and wear masks. Local media reported respiratory issues and skin irritation among residents, with some schools switching to online classes. Volcanic ash worsened air quality in Jakarta, already strained by regional wildfire haze.

The Indonesian agency for meteorology, climatology and geophysics (BMKG) detected ash up to 20,000 feet east of the volcano and at 50,000 feet to the west. Anak Krakatau, formed after the catastrophic 1883 Krakatau eruption, has been sporadically active since then.