It is being said that there are 56 passengers (including five children and a baby) and six crew members onboard the 90-minute flight from Jakarta to Pontianak, the capital of West Kalimantan province on Indonesia's Borneo island. The plane took off from Soekarno-Hatta Airport.
The authorities have started search and rescue operations for the missing plane, a Boeing 737-500, under coordination with the National Search and Rescue Agency and the National Transportation Safety Committee.
The plane lost more than 10,000 feet of altitude in less than a minute, about four minutes after departure from Jakarta, reported flight tracker website FlightRadar24.
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Local media reports said fishermen spotted metal objects believed to be parts of a plane on Saturday afternoon in the Thousand Islands, a chain of islands north of Jakarta. Various television footage showed relatives and friends of people aboard the plane weeping, praying and hugging each other as they waited at Jakartas airport and Pontianaks airport.
Sriwijaya Air is one of Indonesias discount carriers, flying to dozens of domestic and international destinations.
In October 2018, a Boeing 737 MAX 8 jet operated by Lion Air plunged into the Java Sea just minutes after taking off from Jakarta, killing all 189 people on board. It was the worst airline disaster in Indonesia since 1997, when 234 people were killed on a Garuda flight near Medan on Sumatra island.