The crash of a new, Russian-made jetliner into a jagged, Indonesian volcano during a flight to impress potential buyers threw doubt on dozens of plane sales just as Moscow seeks a comeback in foreign markets.

All 45 people aboard were feared dead.

Search and rescue teams climbed through the mist-shrouded, jungly terrain for nearly 20 hours to reach the site where the plane roared in at nearly 800kmh Wednesday, exploding and raining debris down a nearly vertical slope.

When the weather clears, bodies will have to be hoisted by nets and ropes onto hovering choppers, said Gagah Prakoso, a spokesman for the national search and rescue agency.

"We're still searching for survivors," he said. "But it doesn't look good."

The Sukhoi Superjet-100 — Russia's first new model of passenger jet since the fall of the Soviet Union two decades ago — was supposed to kick-start the nation's efforts to modernise its fleet and resurrect its neglected aerospace industry.

Indonesia, the fourth stop of a six-nation "Welcome Asia!" tour, was one of Sukhoi's brightest hopes, accounting for a big chunk of the 170 orders taken globally so far.

Kartika Airlines, Sky Aviation and Queen Air — among dozens of airlines to have popped up in the nation of 240 million to meet the growing demand for cheap air travel in the last decade — together were aiming to buy at least 48.

"Our plan is to order 30 planes, gradually until 2014, to strengthen our fleet," said Arifin Seman, one of the top executives at Kartika. "But we will wait for the result of the investigation before making any further decisions."

Krisman Tarigan, president-director of Sky, which has placed orders for 12 planes, agreed.

"It's too early to say," he said. "But we wouldn't rule out cancellation if it turned out the crash occurred because the plane was not airworthy."

Russia jumped to the Superjet's defence.

"This all is sad and tragic," Dmitry Rogozin, deputy prime minister in charge of the military industries, told Itar Tass news agency, saying pilot error was likely to blame.

"The aircraft has a great future," he said, insisting that the brand new plane flew "without a glitch."

The ill-fated Superjet was carrying dozens of representatives from local airlines and journalists on what was supposed to be a quick, 50-minute demonstration flight Wednesday. Some excited passengers snapped pictures of themselves smiling and waving in front of the twin-engine jet before lifting off, then quickly posting them as profile pictures on Facebook and Twitter.

Just 21 minutes after takeoff from a Jakarta airfield, however, the Russian pilot and co-pilot asked for permission to drop from 3000 metres to 1800m, said Daryatmo, chief of the national search and rescue agency.

They gave no explanation, disappearing from the radar immediately afterward.

It was not clear why the crew asked to shift course, especially since they were so close to the 2200m volcano, or whether they got an OK, Daryatmo said.

Communication tapes will be reviewed as part of the investigation. It's unlikely they will be released to the public any time soon.

The plane, with a relatively low price tag of around US$35 million (NZ$44m), seats from 70 to 98 people and has an operating range of around 4500 kilometres.

It is seen as a potential challenger to similar-sized aircraft from Canada's Bombardier Inc. and Brazil's Embraer SA.

Future buyers will scrutinise the crash investigation for signs of flaws in the aircraft, said Tom Ballantyne, a Sydney-based aviation expert.

"If it's a technical fault ... then obviously that will be very serious for them," he said. "But if it's pilot error or the fault of air traffic control, it won't be quite so bad because they'll be able to say, 'Well, it's not the airplane.'"

The Superjet made its inaugural commercial flight in April last year.

Fitch Ratings agency said in a statement that it expects the crash to "negatively affect" Sukhoi orders for the short term.

"The accident represents a further setback to the ambitious Russian civilian aerospace industry," it said, adding that the success of the Superjet "is especially important as it is the first of many new commercial aircraft to be launched."

Since entering into commercial service, "it has suffered from a three-year development delay, poor initial market reception and minor operational difficulties," it said.

All but 10 of the 45 people on board the plane Wednesday were potential buyers and journalists, said Sunaryo from PT Trimarga Rekatama, the company that helped organize the event.

The others were Russians, all from Sukhoi companies, an American consultant with a local airline and a Frenchman with aircraft engine-maker Snecma.

- AP