A Russian helicopter crashed shortly after takeoff in Siberia on Saturday, killing all 18 people aboard, its airline said.
Preliminary information indicated that the aircraft's blades collided with another helicopter that had taken off beforehand from the same pad in Vankor, above the Arctic Circle about 1,600 miles northeast of Moscow, UTair said in a statement.
There were 15 passengers and three crew aboard the Mi-8 helicopter, the airline said. The second helicopter landed safely, it said.
Russian news reports said all passengers were believed to have been working for a subsidiary of the state oil company Rosneft.
UTair, one of Russia's largest airlines, operates an extensive fleet of helicopters serving Siberian oil fields as well as fixed-wing flights within Russia and to international destinations, mostly in former Soviet republics.
The helicopter that crashed was manufactured in 2010 and the pilot had nearly 6,000 hours of experience, including 2,300 as a captain, the UTair statement said.
Russian air safety has improved since the 1990s, when poor aircraft maintenance, pilot training and official oversight in the wake of the collapse of the Soviet Union resulted in a high crash incidence.