Family members, many of whom spent a long, sleepless night at the airport, broke down in tears on hearing the news. Others stared blankly ahead in disbelief.

The Sukhoi Superjet-100, Russia's first new passenger jet since the fall of the Soviet Union two decades ago, was scattered on a steep near the top of Mount Salak, a volcano just 30 miles (50 kilometres) southwest of Jakarta. The company's blue-and-white logo peeked through the dense canopy of trees.

The location will hamper efforts to evacuate victims, said Gagah Prakoso, adding they will have to be pulled to a hovering helicopter by ropes and nets.

The plane left Halim Perdanakusuma Airport in the capital Wednesday for a quick test flight aimed at impressing potential buyers.

Twenty-one minutes after takeoff, the crew asked for permission to decline from 10,000 feet to 6,000 feet (3,000 metres to 1,800 metres), said Daryatmo, chief of the national search and rescue agency.

The plane fell off the radar immediately afterward.

It was not clear why the Russian pilot and co-pilot asked to drop down, especially when it was so close to the 7,000-foot- (2,200-meter-) high mountain, or if they got the OK.

Tapes between the pilots and air traffic control are being reviewed as part of the investigation, said Tatang Kurniadi, chief of the National Commission on Safety Transportation.

They will not be released to the media any time soon, he said.

More than 1,000 people, including soldiers and police, took part in the search and rescue efforts Thursday.

Eventually,helicopters carrying out aerial surveys spotted the wreckage.

"They have clear view," said Prakoso. "There is no sign of any of the passengers .... We're trying to move in closer to the wreckage now but its reachable only by foot."

Russia's aerospace industry was badly undermined in the economic turmoil following the 1991 collapse of the Soviet Union.

The Superjet — developed by the civil aircraft division of Sukhoi with the co-operation with Western partners — has been widely considered the country's chance to regain a foothold in the international passenger plane market.

Its "Welcome Asia!" tour, which also included stops in Pakistan, Myanmar and Kazakhstan, was intended to drum up support.

Sunaryo from PT. Trimarga Rekatama, the company that helped organize Wednesday's event, said 47 people were on board, many of them potential buyers and journalists.

Among them were eight Russians, all from Sukhoi companies and 37 Indonesians.

An American consultant with Indonesia's PT. Sriwijaya Airline and a Frenchman with aircraft engine-maker Snecma also were on board.

The Superjet — a 75- to 95-seat plane — was being touted as a challenger to similar-sized jets from Canada's Bombardier Inc. and Brazil's Embraer SA.

It made its inaugural commercial flight last year.

"It is their big hope that they will somehow get into the jet aircraft passenger market in a bigger way than they have, because we all know that the Russians have had a dreadful record in the past with their aircraft, so this was vitally important to their industry," said Tom Ballantyne, a Sydney-based aviation expert.

With a relatively low price tag of around $35 million, the plane has garnered around 170 orders. And Indonesia, a sprawling archipelagic nation of 240 million people with a fast-growing middle class, was one of the biggest potential customers.

Kartika Airlines and Sky Aviation — among dozens of airlines to have popped up in Indonesia in the last decade to meet the growing demand for cheap air travel — had already ordered at least 42.

People involved in those plans said they were waiting for the results of the investigation before reconsidering. Most wanted to know whether the problem was mechanical or pilot error. AP