AirAsia Indonesia flight QZ8501 reportedly lost contact with air traffic control over the Java Sea, between the islands of Kalimantan and Java.
The Indonesian air force said two of its planes had been dispatched to scour an area of the Java Sea, southwest of Pangkalan Bun in Kalimantan province.
Here are five things to know about the area:
1. Java Sea is a part of the western Pacific Ocean between the Indonesian islands of Java and Borneo. It is bordered by Borneo on the north, Java on the south, Sumatra on the west, and the Flores and Bali seas on the east. It is linked to the Indian Ocean by the Sunda Strait.
2. It has shallow waters, with an average depth of about 46 metres. It covers a total surface area of 167,000 square miles, or about 603 Singapores (Singapore's land area is about 277 square miles).
3. The area is mainly influenced by monsoon climate. The rainy monsoon, which occurs between mid-December and March, is characterised by very windy periods with frequent rainfalls lasting for days. The dry monsoon occurs from June to September.
4. There have been several incidents involving planes and ships in the area.
On Jan 1, 2007, a plane of the now-defunct Adam Air lost contact with air traffic control while it was flying over the Java Sea. The Boeing 737-400, which carried 102 people mostly from Indonesia, was on its way from Surabaya to Manado.
Parts of the plane were found only 10 days later off the west coast of Sulawesi. Investigators found that the pilots had accidentally disconnected the autopilot system while trying to fix a problem in the navigation instruments.
In May 2009, an inter-island ferry caught fire in the Java Sea. Some 350 passengers and crew were rescued by a passing cargo ship.
In December 2006, a crowded ferry broke apart and sank in the Java Sea during a violent storm, killing more than 400 people.
In 1981, 580 people were killed when Indonesian passenger ship Tamponas II caught fire and sank in the area.
5. Wrecks of ships are reportedly still in the Java Sea, which is also a popular underwater dive spot.
It was the scene of one of the costliest naval battles of World War II, dubbed the Battle of the Java Sea. The naval forces of the Netherlands, Britain, Australia, and the United States were nearly destroyed trying to defend Java from Japanese attack.
In August this year, the US Navy confirmed that a wreck found at the bottom of the Java Sea is the USS Houston, a cruiser sunk by the Japanese in World War II. The wreck is the final resting place of as many as 700 US sailors and marines.
Wreck of a ship called Indono that sank in 1955 is also still in the Java Sea, near the waters of Karimunjawa, said reports.
Source: Nasa's Earth Observatory, Encyclopedia Britannica, BBC News