On July 5, 2025, an Il-54 aircraft, registration RA-2860G, was prepared for a training flight from Gostilitzy Aerodrome. During pre-flight preparations, the aircraft was refueled with 200 liters of what was intended to be AI-95 grade gasoline, bringing the total fuel quantity to 260 liters (190 kg). No engine oil was added during this process.
The aircraft commander reviewed meteorological conditions via the 'Windy' website and determined that the weather did not preclude the planned flight. Because the airfield lacked medical personnel, the commander assumed responsibility for the crew's fitness to fly, as permitted under FAP-128 regulations. The flight included the aircraft commander and two passengers, one of whom was the aircraft owner.
At 08:41, the aircraft took off from Gostilitzy Aerodrome. While the commander did not possess individual authorization to operate the aircraft, the presence of the owner on board satisfied the requirements of FAP-128 clause 2.20.
Subsequent laboratory analysis of fuel samples taken from the left and right fuel tanks of RA-2860G revealed that the fuel was automotive gasoline with an octane number of only 86-87. This failed to meet the AI-95 grade requirement. The study noted that the service manual for the engines recommends against using gasoline with a research octane number below 95.