Indonesia today requested foreign assistance in the agonising and mysterious search for a passenger aircraft and its 102 people on board who have been missing since Monday night.

The search for the Adam Air jet, a Boeing 737, began more than 48 hours ago, as soon as the pilots sent two distress signals in heavy rain mid-way through a two-hour flight from Indonesia's main island of Java to Manado, a town in northern Sulawesi.

Since then, hundreds of soldiers and rescue officials, as well as ships and five military aircraft have been despatched across a broad triangle of jungle, mountain and sea in the western reaches of Sulawesi, looking for the wreckage.

Yesterday, aviation officials and a spokesman for Adam Air, a budget airline, exacerbated the unease of those waiting for news by mistakenly announcing that the aircraft had been found, along with 12 survivors.

Today the co-ordinators of the search effort renewed their attempts to find the jet — continuing to scour the mountains while sending three Indonesian navy vessels in the Makkasar Strait after Singaporean authorities suggested that the aircraft's last position was in the sea — but admitted as night fell that not a trace of the 36-metre-long (120ft) plane had been found.

"Until now, we have not yet found any signal or indication of where the ill-fated plane crashed," said Rear Commander Eddy Suyanto, an Indonesian Air Force official helping lead the hunt.

"God willing, we can find it soon," said Bambang Karnoyudho, the head of the National Search and Rescue Agency.

Chief Air Marshal Djoko Suyanto told journalists in Jakarta that the Indonesian Government had asked Singapore and America to help find the aircraft. A team from the US National Transportation Safety Board is expected to arrive in the country tomorrow. Three of the 102 people missing are believed to be Americans.

Aviation experts said today the jet's emergency beacon could have been damaged in the crash or that its signal might be being blocked if the aircraft has been buried in steep jungle or far out to sea.

"In an area of low population density, particularly if it is in inhospitable terrain — such as jungle, or a deep ravine or covered by a canopy — it could sit for a long time without being found," said Laurence Benn, head of the Center for Civil Aviation in London.

The ongoing search, and initial error in reporting that the jet had been found, has caused anger among the relatives of those who were on board, many of whom have been waiting for two days at Manado Airport.

The distress comes as the country continues to learn details of last Friday's ferry disaster, which killed more than 400 people, and was the worst of a series of accidents, including shipwrecks and landslides, that Indonesia has suffered in weeks of torrential rains.

Today a group of 12 survivors from the Senopati Nusantara ferry, which went down in heavy seas with more than 600 people on board, described the sinking and their attempts to stay alive as they spent four days floating on wreckage and an empty oil rig in the Java Sea.

A man called Suyatno was picked up with his six-year-old son around 200km (120 miles) from where the accident took place. "Even though I was weak, I never let go of my boy and held him tight," he said today. "In the rolling seas, I never let him out of my sight and am now grateful to be on land."

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