If bad dudes have done this then the no contact from them is very disturbing. Two possibilities are ;
- they are taking time to spread the hostages far and wide to stop any chance of rescue , or
- they want the aircraft and hostages intact for a secondary purpose eg A B777 cargo hold would any type of mass weapon you could imagine. If the aircraft turned up somewhere and announced we have the hostages we are going to XYZ. It would take a very brave leader to say no, and splash it before it reached the intended target.
Far fetched??? maybe.....but bad dudes have a record for creative thinking in a very twisted way.