At least 12 flights from Jakarta's Soekarno-Hatta airport to Surabaya's Djuanda airport have been cancelled so far on Friday due to the eruption of Mount Kelud in East Java, said general manager of Soekarno-Hatta with state airport operator PT Angkasa Pura II Yudis Setiawan.
Airports in Solo, Malang, Surabaya and Yogyakarta remain closed.
The 1,730-meter tall volcano erupted on Thursday night spreading volcanic ash as far as Magelang in Central Java, more than 120 kilometers away.
The eruption sent local residents fleeing to safer areas, local authorities said.
Yudis said he could not say when flights could be resumed, but it could take days depending on the the status of the eruption.
Among the airlines canceling flights are Garuda Airline, Lion Air, Citilink, Air Asia and Sriwijaya Air.
Yudis said the number of cancelled flights could increase, adding that passengers had already been notified.