Soekarno-Hatta International Airport suspended flight operations on Sunday due to volcanic ash, the airport posted on Instagram, stranding hundreds of passengers at the facility.
The suspension has affected 301 flights, including 58 international flights, airport operator Angkasa Pura said in a statement.
Singapore Airlines said it had cancelled flights to and from Jakarta for the rest of Sunday.
Anak Krakatau, roughly halfway between Java and Sumatra in Indonesia's vast island chain, has been erupting since late Friday, with volcanic ash detected at the airport early on Sunday, the transport ministry said.
Ash reached as high as 6000 metres on the Java side of the volcano and 15,000 metres on the Sumatra side and some parts of Banten province in Java, the meteorological agency BMKG posted on its website.
After one domestic flight was cancelled, Suhardi, 58, made his way to Soekarno-Hatta, hoping to catch a connecting flight to Samarinda on the Indonesian part of Borneo island in the morning.
"I thought Jakarta-to-Samarinda still available - apparently it is also cancelled," Suhardi, who goes by one name, told Reuters.
French national Eloan Tasset, 21, got a text from Batik Air that his flight to his holiday destination of Manado in North Sulawesi had been delayed, but he said it was unclear how long the delay would be.
"If they tell me my flight is cancelled, I think I'm going to try to find a hotel in Jakarta," he said.
The airport operator said it was providing food and light refreshments for affected passengers and buses to hotels, in co-ordination with the airlines.
The disaster mitigation agency BNPB said it would conduct a weather modification operation, which could include cloud-seeding, on Sunday to promote rain.
"If it rains heavily enough, the volcanic ash that has been disrupting our daily lives since yesterday and continuing today will be washed away quickly," BNPB chief Suharyanto told reporters.
BNPB urged people to remain calm and increase vigilance.
"In the event of ashfall, people are advised to wear masks and eye protection, reduce outdoor activities, cover water sources and exercise caution when driving, as volcanic ash can reduce visibility," spokesperson Berton Panjaitan said.
Ferries in Sunda Strait were operating normally, the transport ministry said, urging vessels to stay at least 3km from Anak Krakatau's crater and remain vigilant for volcanic hazards, including volcanic ash and other ejected materials.
Several schools cancelled activities on Saturday after students and residents suffered eye irritation from the ash, while fishermen cancelled fishing trips, local media outlet Kompas reported.
Some 850km from Anak Krakatau, Mount Semeru in East Java also erupted on Sunday, sending an ash column 1km above the summit, volcano monitoring agency PVMBG said.
It advised residents to stay at least 5km from the crater and warned of the risk of hot ash clouds and lava flows up to 17km from the summit.
Indonesia sits on the Pacific "Ring of Fire", where earthquakes and volcanic eruptions are frequent.
Anak Krakatau has been on alert level three, the second-highest, since July 2.
The disaster mitigation agency said there was no imminent risk of tsunami from the volcano.
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