Indonesian rescuers waited for daylight Thursday to intensify the search for a Russian Sukhoi Superjet 100 with about 50 people aboard that went missing during a demonstration flight.
The plane disappeared from radar screens south of the capital Jakarta 50 minutes into what was meant to be a brief flight on Wednesday.
Rescue teams were headed on foot by early Thursday towards Salak mountain, where the plane went missing, with officials saying helicopters would join the search after dawn.
"So far we still have not found the plane. I cannot confirm but there is a possibility that it could have crashed," said Ketut Parwa, the capital's search and rescue agency chief who is coordinating operations.
"If it had made an emergency landing we should have received some news via the radio or phone calls by passengers by now," he told AFP.
Two helicopters searching for the plane Wednesday evening were forced to turn back due to strong winds and bad weather, and Parwa said choppers would be sent out again after sunrise.
By midnight Wednesday, hundreds of rescuers had set up three posts around the mountain, one of them close to the town of Cidahu.
Parwa said that closer to dawn, they would travel by trucks some 7.5 kilometres (4.6 miles) from Cidahu, then trek up steep mountain slopes.
"We fear it might have crashed in a jungly area some 2,000 metres (6,500 feet) above sea level near Kawah Ratu," a crater in the area, he added.
There were scenes of grief at the airport in Jakarta late Wednesday, with relatives of some passengers sitting on luggage carousels weeping uncontrollably, waiting on tenterhooks for information about the missing plane.
Reports of the exact number on board varied, with local rescue officials saying it was carrying 46 people and Trimarga Rekatama, the company responsible for inviting the passengers, saying 50 were on board.
Herry Bakti, head of the aviation division of Indonesia's transport ministry, said the Superjet was on the second of two demonstration flights, and those on board were invited guests.
A list of 36 passenger names showed most were Indonesian airline and aviation officials, plus five journalists and a representative of French aircraft engine maker SNECMA.
The French embassy in Jakarta confirmed there was one French national aboard.
The Superjet made its first commercial flight last year and if a major accident is confirmed it would be the first disaster to involve the aircraft.
The Superjet 100 is a new passenger aircraft built by legendary Russian planemaker Sukhoi in an attempt to lift the country's civil aviation industry from a post-Soviet crisis.
The plane took off at 2:00 pm from east Jakarta's Halim Perdanakusuma airport, which is used for some commercial and military flights.
It descended from 10,000 feet (3,048 metres) to 6,000 feet 50 minutes into the flight, then disappeared over the 7,200-foot (2,200-metre) Salak mountain.
Russia's RIA Novosti news agency reported 36 non-Russians on board and eight Russians, four of them crew and the others Sukhoi company representatives. It named the captain as Alexander Yablontsev, 57, a veteran pilot.
The Superjet, crucial to Russia's hopes of becoming a major player in the modern aviation market, is a joint venture between Sukhoi and Italy's Alenia Aeronautica.
So far it is being flown by two airlines, Russia's Aeroflot and Armenia's Armavia, but orders have been confirmed with more, including Indonesia's Kartika Airlines and Sky Aviation, state-run news agency Antara reported.
The demonstration flight in Indonesia was part of an Asian roadshow to promote the aircraft. It earlier took in Kazakhstan and Pakistan, and was due to go on to Laos and Vietnam.
Aeroflot has had trouble with its Superjets, with its first one spending several weeks grounded upon delivery because of an air conditioning problem, and in March, a plane had to cut short a flight after encountering problems with its undercarriage.