Hijacking has a clear purpose meditrina. This is not comparable to your normal hijack. They make demands, they have bombs and everyone knows about it. No less awful but authorities and families at least know where they stand.
Here there is nothing, although I suspect they must know more than has been let on, perhaps to avoid mass hysteria, I don't know. Someone has stolen a plane and deliberately kept it quiet. The fact that it is even possible to do this after all the attacks on aviation is horrendous. No one knows why, which at the moment makes it also just as hard to try and prevent it from happening again.
And in the meantime families have to live with the knowledge that their loved ones might have been kept in fear for hours on end and still have no clue what happened to them. As for the passengers what they must have gone through... I have no words.