As an immense search for Indonesia's missing passenger plane intensified on Sunday, records show that a string of aircraft have never been found in the archipelago nation after disappearing.
The Adam Air plane with 102 passengers and crew vanished off radar screens on January 1, halfway through a flight from Surabaya on Java island to Manado on the northeast tip of Sulawesi island.
A huge air, sea and land search has been frustrated by bad weather, rugged terrain and uncertainty over where the Boeing went down.
But aviation records show that difficulty in finding missing planes is not unusual in the vast archipelago nation stretching over 5,000 kilometres (3,100 miles).
Following are other examples of planes that have disappeared from sight and which, records show, have never been found.
-- A Garuda Indonesia Airlines plane with 21 passengers and five crew on board disappeared in 1961 near the island of Madura.
Despite an extensive search, the DC-3 plane, which had been flying from Surabaya to Balikpapan on the eastern Indonesian part of Borneo island before it presumably crashed, was never found.
-- More recently in 1995, a Merpati Nusantara Airlines plane with 14 people on board was never found. The Twin-Otter plane went missing en route from Bima on Sumbawa island to Ruteng on Flores island on January 19, 1995.
-- A chartered Pan Malaysia Air Transport plane carrying 16 people disappeared 35 minutes after take off from Medan in North Sumatra bound for Banda Aceh, the capital of Aceh province, on January 30, 1993.
-- A Bolkow BO-105 army helicopter went missing shortly after take-off from Medan in North Sumatra on August 22, 1994.
-- The first husband of former Indonesian president Megawati Sukarnoputri, airforce first lieutenant Surindro Supjarso, and his T-701 airforce aircraft went missing in Biak, Papua, in 1970.
Even when a plane is reported missing, it can be days -- or years -- before its wreckage is found.
-- A Bouraq Indonesia Airlines plane disappeared in Papua on August 9, 1995 with 10 people on board, but the wreckage of the Hawker Siddeley HS-7482A was found five days later on a steep mountain slope. There were no survivors.
-- Angkasa, an Indonesian magazine on aviation, reported back in 2000 that wreckage from a Piper PA-23 aircraft that went missing while flying over Aceh in 1970 was only found eight years later in the jungles of North Aceh.
