Russian airline Kogalymavia, whose Airbus A321 crashed in Egypt's Sinai Peninsula on Saturday killing all 224 people on board, said Monday that the plane must have been damaged by an external force, as it could not have spontaneously broken apart in the air.The airline's deputy director, Viktor Yung, was quoted by RT as telling media on Monday that the crew of Flight 7K9268 was apparently disabled before the aircraft began its rapid descent that brought it crashing down in Sinai. "As the catastrophic incident started to develop, the crew members were rendered completely incapable. This explains why they didn’t attempt to contact air traffic and report the incident happening on board," he said. "The only possible explanation is a mechanical force acting on the aircraft,” Aleksand Smirnov, who supervises the company’s fleet, was quoted by RT as saying. "There is no combination of system failures that could have broken the plane apart in the air.""The plane was in excellent condition," Smirnov said. "We rule out a technical fault and any mistake by the crew," he said.A source in the committee analyzing the black box recorders from the airliner said that it was not struck from the outside and the pilot did not make a distress call before it disappeared from radar. The source declined to give more details but based his comments on the preliminary examination of the black boxes recovered from the flight. A civil aviation ministry source said earlier that the analysis of the flight recorders was ongoing.Kremlin's spokesman Dmitry Peskov said on Monday that there are not yet any grounds to rule out any theory for the crash of the Russian airliner in Egypt, including terrorism.The Sinai Province, the Islamic State's affiliate in Egypt, has claimed responsibility for causing the crash, although the claim has not been verified.Russian Prime Minister Dmitry Medvedev called on Monday for a thorough investigation into the plane crash."The key task is to investigate in detail what caused the tragedy," Medvedev said in remarks showed by Rossiya-24 state television.