The Ukrainian Defence Ministry's Main Intelligence Directorate has named the cause of the Su-30SM jet crash in Irkutsk, Russia.
According to it, it crashed due to the poor quality of repairs.
It said that two Su-30SM conducted flight tests over Irkutsk after the repair work.
"One of them landed at the airfield after fulfilling the flight plan, the second remained in the air, and the crew did not get in touch for 20 minutes. The first plane took off again and approached the aircraft in distress. The pilots visually confirmed that the crew of the emergency plane died, probably due to a faulty oxygen system. After running out of fuel, the faulty plane crashed on a residential building in the Novo-Lenino district," the Main Intelligence Directorate said.
It added that the cabin was depressurized, the crew could not eject, which led to the death of both pilots.
On 23 October, a Su-30 fighter jet crashed into a two-story building in the Russian regional centre of Irkutsk. A fire broke out at the crash site over an area of 200 sq m.