I think it was hijacked and crashed into the sea because information has claimed debris of the plane has been found floating in the sea. Two men had stolen passports and when they hijacked the plane they crashed it into the water. There is no doubt that the debris found in the water is from the plane that crashed into the sea.
I think that it was hijacked because it has been reported that the plane was seen on military radar after control tower had lost contact. Another thing that I have heard but I don't know if i is true is that the people's phones who were on the plane are still ringing but no one is answering. But i stress that I don't know if this is true. Over all I think that the plane was hijacked by someone on board who knew enough to turn off the all the systems and then flew the plane for many more hours to an unknown destination. . .