My money is on sabotage on the plane itself, not a missile or suchlike. Some kind of bomb or device which caused the wing to break off.

Footage shows the plane falling vertically and seemed to be missing a wing.

If you absolutely want to crash a plane and kill everyone on board, deleting one of the wings is a pretty surefire way to do it.

It was videoed falling from the sky with one wing missing. Experts are quoted as saying that just doesn’t happen on modern jets without some form of serious attack on it. Also people saw missile trails just before it exploded.