Most aircraft, once retired, are not serviceable for long and used for salvage. Also, to get a plane out of a boneyard or to purchase an aircraft abroad still requires registration and would not be of use to a terrorist organization unless they didn't care about identification. Also, if the plane had ditched (crashed into the sea) the ELT (emergency locator transmitters) would have immediately activated and they aren't something you can get to in flight to deactivate. Much is being made about the ACARS being shutoff. Think of this as nothing more than a fax machine on an airplane. Messages can be sent and received from them and engine status reports are sent to Rolls Royce during flight via this machine. Airlines regularly fly with these completely disabled and are not necessary for safety of flight. You would be surprised how many planes go out without them. It is not normally used for tracking or identification. Transponders or IFF as it is sometimes called generally are used for identification. They can be switched off easily in flight.
Rapid descent doesn't make anyone pass out except on television. Rapid depressurization at altitude can make you lose consciousness due to lack of oxygen anywhere above 10,000 feet but it takes time and you would know something was wrong.
The most important point of the entire thing is the flight path. The aircraft was flown to purposefully avoid detection in known flight paths that had little or no known radar or TCAS coverage(another aircraft identification system that is hard wired into the aircraft electronics system or EICAS).
I obviously cannot say with any certainty what happened but knowing what I know after 24 years working on Boeing aircraft, from what I can gather, that plane was hijacked and ultimately crashed in the Indian Ocean. My immediate thoughts are that it will be found in the next month or so.
JMO
Hope this helps,
FDC
