Could have had a pre-programmed flight plan and programmed to not enable the pilots to disengage the autopilot and disable the radios…
If this was done one might not even have to remote control from another aircraft, just at a certain time, have the autopilot take control and follow another flight plan in the system. You can override the autopilot via the aircraft controls but if the persons responsible went that far they could have done other things to undo pilot inputs. Does Honeywell (the maker of the avionics system give a ‘back-door’ into the system for the spooks?
AW139 pilot (with Honeywell Primus Epic system) and former US Army aviator
Read more at http://investmentwatchblog.com/mh370-possibility-diego-garcia/#6TpWLemPiPG5jCjA.99