more likely a ‘thunderball’ operation.
pilot and copilot were substituted prior to take off.
now pilot and copilot will need positive id prior to boarding the plane.
This is one of the strongest theories, IMO. I believe someone was hiding in the equipment bay near the cockpit.. The ACARS, transponders and just about everything else can be turned off from down there, unbeknownst to the pilots. Can the aircraft be flown from the equipment bay?
The aircraft was hijacked by a stowaway with a knife or gun.