If it was Hijacked and the passengers are still alive, why no ransom demands? It seems odd unless the passengers aren't the thing they were after.
what if they're after the plane. Or a group of passengers on the plane, say the 20 people from the Texas semiconductor company?
Not saying they're are, but you could hijack a plane fro a number of reasons. Not just to hold the people for ransom, which is the usual thing. You might want the cargo, which could be people. Or you might want the plane, or something on the plane. Or you might want to create a situation for whatever reason. Next steps are dependent on their objective and whether they did exactly what they intended to.
And even then, if hijack is the scenario, we're presupposing they reached their intended destination - they might not have. The plane might have been hijacked, by either a pilot(s) and or some third party, then, for whatever reasons crashed into the ocean, not fulfilling the 'mission'.