JAKARTA, Indonesia – Search and rescue teams were scouring the slopes of a dormant volcano in western Indonesia early today for signs of a new Russian-made passenger plane that dropped off the radar while on a demonstration flight. Fifty people were on board, including potential buyers, diplomats and journalists.

Helicopters, earlier forced to abort an aerial survey because of bad weather, were also set to resume their search.

The Sukhoi Superjet-100, Russia’s first new passenger jet since the fall of the Soviet Union two decades ago, has been widely considered the country’s chance to regain a foothold in the international passenger plane market.

Developed by the civil aircraft division of Sukhoi — with the co-operation with Western partners — officials were showing off their 75- to 95-seat plane during a “Welcome Asia” tour that had already included stops in Myanmar, Pakistan and Kazakhstan.

It took off from the Halim Perdanakusuma Airport in Indonesia’s capital, Jakarta, at 2:21 p.m. Wednesday for what was supposed to be a quick test flight — the second of the day.

It dropped off the radar just 21 minutes later, shortly after the crew asked air traffic control for permission to drop from 10,000 feet to 6,000 feet, said Daryatmo, chief of the national search and rescue agency.

They didn’t explain the change of course, which occurred near Salak mountain, he said. Though drizzling at the time, it was not stormy, and there was no obvious sign of distress.

Cellphones of those on board were either turned off or not active.

“I saw a big plane passing just over my house,” Juanda, a villager who lives near the 7,200-foot (2,200-meter) mountain, told local station TVOne.

“It was veering a bit to one side, the engine roaring,” he said. “It seemed to be heading toward Salak, but I didn’t hear an explosion or anything.”

Dozens of family members spent the night at the airport, awaiting news about their loved ones. Many were crying. Some clung to young, sleepy children.

Windy Prisilla said her husband called her early Wednesday to say he was going on the Sukhoi test flight.

“He wanted me to meet him at the airport before they took off so we could have lunch together, but I told him I couldn’t. I had to get the kids to school,” she said, sobbing inconsolably as friends wrapped their arms around her.

“All I can do now is pray to God. I want him back home safely.”