The only reasonable explanation for the crash of a Russian passenger jet in Egypt is "an external influence," not technical or crew error, an executive from the airline that operated the flight said Monday, CNN reported, adding that investigators have played down an apparent claim by Islamic militants in Sinai that they brought down the Airbus A321-200.

"We exclude technical problems and reject human error," Alexander Smirnov, a Kogalymavia airline official, said at a Moscow news conference as he discussed possible causes of the crash, which killed all 224 people on board, CNN claimed.

Contrarily, the Wall Street Journal has reported that aviation experts have speculated that a sudden mechanical failure or an explosion could have been to blame.

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After climbing to 33,000 feet, the jet dropped some 6,000 feet in about 22 seconds, the Wall Street Journal reported, adding that, in roughly 60 seconds, flight data shows that the plane’s speed dropped to about 100 miles an hour, slower than the forward speed needed to continue safe flight.

“This isn’t flying, it’s falling. Apparently, the plane sustained damage before this [and] that became the reason for the fall,” Smirnov was quoted by the Guardian.

"It's disturbing to me. It indicates to me that something occurred possibly in the way of aerodynamic stall. I mean, an airplane just cannot fly at those lower speeds," said CNN aviation analyst Les Abend while fellow aviation analyst Peter Goelz suggested the disaster could have resulted from "some sort of catastrophic failure, perhaps caused by an earlier maintenance problem. It could have been a center fuel tank that might have exploded."

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A militant group affiliated with Islamic State in Egypt claimed responsibility for bringing down the jet, but Egypt and Russia disputed the claim, saying the group did not have the weaponry to hit a flight at that altitude, the Guardian reported.

However, Zack Gold, a regional expert on Sinai security quoted by the Guardian, pointed out on Sunday that the militant’s group’s statement “said they were responsible for downing the plane, not shooting it down.”

Gold was quoted by the Guardian: “A legitimate ISIS-supporting account in Sinai said, ‘Why is everyone talking about shooting it down, why is no one talking about a bomb or suicide bomber on board.’”