YankeeJim:Is it possible for a pilot or knowledgeable type to disable systems while in the air so the plane basically can fly incognito, like a Stealth fighter?
Pretty much, yes it is possible, but on a passenger jet? No valid reason. Especially if you access the E/E Bay it is possible to fly as an unknown aircraft. This is why I am sure back up system will be deployed in the future.
But to not be visible to a primary radar is not so easy (provided some observance by the controller is assumed. To fly at low altitudes for prolonged periods, particularly in poor visibility and assuming a very good knowledge of the terrain is difficult and still is not immune to detection.
Personally I have heard this flight had altitudes between FL50 and FL450. Prior is possible the latter exceeds the parameters of safe operating levels. But the supposed decent of 40000 feet in one minute is not possible without breaking up IMO.
As I said we have not been told the full story, and understandable to a high degree. But the press have had a field day. But the T7 took the Northern route, either to may military personnel were asleep or were complicit in the "disappearance".
I think and initially thought after day one, this was another Egypt or Silk Air. I spoke to a mate who knew of (did not know) the commander and only spoke very highly of him, so that leaves the F/O or a takeover of unknowns, or it was a cascading malfunction (cough cough).
Sadly just to many unknowns so I hope that we do get conclusive answers soon.