Two Russian air force pilots died on Tuesday in a crash of one of the country's mainline fighter jets, army spokesmen said, DPA reported.
Officials were blaming a technical problem in a MiG-31 interceptor for the apparent accident, which took place in the central Siberian Perm district.
News reports described the pilots as experienced airmen. They had been on an early morning training flight.
Russian air force command ordered all MiG-31 aircraft grounded pending determination of the exact cause of the crash.
Investigators also were checking whether the pilots had violated flight instructions, Interfax reported.
The plane crashed in a ravine some 11 kilometres from the village Bolgary. Villagers suffered no injuries and there was no damage to property, said Perm region governor Oleg Chirkunov.
The MiG-31 is Russia's mainline interceptor fighter. A plane designed to climb quickly and travel at high speeds, its primary mission is protecting the country's airspace from encroaching aircraft.
Russia operates between 280 and 380 MiG-31s, according to defence industry estimates.