[Z]

I'd say it's likely that they were all killed on impact if they weren't already dead before the plane crashed - smashing into the water at that speed will have ripped the plane apart and either pressure would have killed them or the rush of water would have drowned them all immediately. Still reckon that there was a fire on board the plane which knocked out all their communications systems so the pilot turned it as a last ditch effort to try and reach the nearest airport but they all passed out and died from smoke inhalation and the plane just kept flying towards the open ocean and eventually ran out of fuel and crashed. A combination of it crashing in the middle of nowhere, being totally off course and the sea conditions have all contributed to the plane sinking, debris likely spreading or the plane being so burned out that there's barely any debris anyway and they'll probably not find it for a very long time.