Technical fault, human error and an impact from outside have all been excluded as possible causes of the tragic crash of Russian Airbus A321 that went down on Saturday in Egypt.
The 18-year old aircraft operated by Metrojet disappeared from air-traffic control radars 23 minutes after take-off, killing 224 people aboard, most of them returning from holidays in Sharm el-Sheikh.
The cause of the crash of the St Petersburg-bound plane remains unknown. After a preliminary investigation of the jet’s recovered black boxes, an investigator told Reuters the plane was not struck from outside, but declined to give further details.
According to Russian officials, the plane broke up mid-air before crashing down on the Sinai Peninsula.
"The plane was in excellent condition," Alexander Smirnov, deputy general director of Kogalymavia which owns the Metrojet brand, said during a press conference in Moscow. "We rule out a technical fault and any mistake by the crew."
According to Russian media, the crew recently passed medical tests and the plane’s engines - manufactured by the International Aero Engines consortium - had undergone inspection in Moscow on October 26 2015, which didn’t indicate any problems.
The aircraft had received a certificate of airworthiness earlier this year from regulators in Ireland, where it was registered.
Smirnov said there had been no emergency call from the pilots to services on the ground during the flight.
According to Egypt’s Civil Aviation Ministry, the plane’s track was lost when it was at the altitude of 9,400m. Sweden-based flight-tracking service FlightRadar24 said its data suggest the jet was rapidly descending before losing contact with the ground.
The A321, a medium-haul jet, has a good safety record. The destroyed plane has been operated by Metrojet since 2012 and had 56,000 flight hours combined from nearly 21,000 flights.
According to Russian media, Russian transport prosecutors have already examined the quality of the fuel used by the airliner and found that it met necessary requirements.
Russian and French aviation experts are cooperating with the Egyptians on the investigation and examination of the black boxes.
An Egyptian militant group affiliated with the Islamic State said on Saturday that it had brought down the plane, but experts have doubted the veracity of the claims as Islamic militants are believed not to own missiles capable of hitting a plane at a cruising altitude.
Russia and other former Soviet republics have poor air safety records, notably on domestic flights. Some accidents have been blamed on the use of ageing aircraft, but industry experts point to other problems, such as poor crew training and lax government controls.
Russian Airbus A321 infographic