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Above is a picture of the exact plane that crashed.
While im not an aircrash investigator, i will say this accident reminds me of the plane crash that killed pro golfer Payne Stewart.
That accident that occured in 2001 happened when the plane became decompressurized during flight. Eventually the plane ran out of fuel and crashed in South Dakota, 1300 miles from its intended landing.
This accident doesnt seem to be a terrorist act also, but it should be known that Greece's airport security lacks in comparrison to the US's (Maybe they dont make you take your shoes off in Greece)