Solving this one could prove very difficult. There should be some radar tapes that would shed light on whether the plane was shot down accidentally. That would be the first place to start. While the plane is in very deep water, this isn't the first time when a black box (actually, they're orange) was recovered from that deep. In the 1980s, an Air India 747 (Flight 182) crashed mysteriously off the coast of Ireland in water 6,000 feet deep. It took a while, but the boxes were recovered and proved the plane had been brought down by a bomb.

While the security at Israeli airports is extremely tight, it doesn't preclude something being smuggled onto the plane before it flew to Israel. There is a possibility that someone could've planted a bomb set to go off at another time days, even weeks before the crash. It would have to well hidden but there are a lot of nooks and crannies on any airliner. I don't know for sure but I don't think Israeli security officers sweep every plane that lands at their airport for incoming bombs. I could well be wrong about that. Israeli security is tight and they don't discuss details.