Ash from Anak Krakatau, which sits halfway between Java and Sumatra islands, has blanketed Jakarta and several surrounding areas since it erupted late on Friday, leading to the closure of the airports for safety reasons.
At night, the lava from Anak Krakatau lit the sky red as it erupted. Residents were sweeping the dusty floors of their homes and the blackened walls of a nearby mosque.
Anak Krakatau is one of about 130 active volcanoes in Indonesia, which straddles the "Pacific Ring of Fire", a highly seismically active zone where different plates on the earth's crust meet to create a large number of earthquakes and volcanic eruptions.
Anak Krakatau, which means child of Krakatau, began emerging a century ago from the area previously occupied by Krakatau, then known as Krakatoa. The older volcano destroyed itself in mass eruptions in 1883, which killed more than 36,000 people after triggering a series of tsunamis.
A tsunami after an eruption at Anak Krakatau in 2018 killed over 400 people.
The transport ministry said on Monday more than 270,000 people have been affected by the delay, diversion, or cancellation of 2300 flights.
Jakarta's main airport will remain closed until 6pm on Monday (9pm AEST), the ministry said, along with six other airports. One other airport in South Sumatra has been reopened.
"We cannot ascertain when this will end due to the dynamic weather," Transport Minister Dudy Purwagandhi said in a statement on Monday.
Passengers at Jakarta's main airport, the Soekarno-Hatta, which is located in the city of Tangerang adjacent to Jakarta, were scurrying around, frantically looking for their flight status on the information boards. Some were sleeping on benches.
Carlos Zabala, 24, was travelling to his native Spain after a holiday when he learned his flight was repeatedly delayed. Expressing his frustration, he blamed operators for the lack of clarity.
"All we have to do is wait, and wait, and wait," he said.
Renowned volcano expert Surono told Reuters that windy and dry conditions were blowing the sulphur and silica-laden ash all over the place, and could pose risks to plane engines.
"For Anak Krakatau, the recent eruption was unusual," he said.
The volcano monitoring agency's website showed the most recent Anak Krakatau eruption occurred on Sunday night.
The agency warned on Monday that "the probability of further eruptions in the coming periods remains high".
The eruptions have seen ash towers reach as high as 6000 metres on the Java side of the volcano and 15,000 metres on the Sumatra side and in some parts of Banten province in Java, meteorological agency BMKG posted on its website.
On Sunday, the disaster agency called for people to wear masks while travelling outdoors to avoid breathing in the ash. In Jakarta and Lampung, schools will use remote learning to counter health risks for students, state news agency Antara reported.
with AP
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