A new Russian commercial jet went missing Wednesday in the mountains of Indonesia and is presumed crashed during a demonstration flight for airline buyers.

The Sukhoi Superjet-100 disappeared from radar 21 minutes into its 50 minute flight after taking off from Jakarta’s Halim Perdanakusuma Airport at 2:21 pm their time. Just prior to its disappearance the flight crew, while near the Salak Mountain range, asked air traffic control for permission to descend to a lower altitude. There was no explanation for the change of altitude or course.

A villager living near the mountain said that the aircraft flew over her location very low, veering, with the engines roaring. When it was observed it was heading in the direction of the mountains.

Aboard were buyers from the major airlines in Indonesia as well as diplomats and journalists covering the event.

Bad weather turned at least two of the search helicopters back from the mountains Wednesday and the air search was called off as night fell. Ground searches by soldiers, police and members of the air force continued however, but the terrain is tough and the going slow.

Rear Marshal Daryatmo, who is the chief of Indonesia,s search and rescue said “Hopefully they’ll be able to reach the location tonight.”