A couple of comments inspired by some previous posts...............
Its not possible to track vehicles be they ships or aircraft over the oceans WITHOUT
electronic assistance ro the said vehicle. Which means such assitance can always disabled by people in the said vehicle.
ATC always use secondary radar which relies on a transponder in the vehicle. Secondary or the older reflective radar has a number of serious limitations. First its line of site only, hills, curvature of the earth even rough seas can hide a target no problems. Second it ONLY
shows the presence of at target it DOES NOT
provide any identification. Two methods are used to enable a target to be identified, the first is if one is being controled by primary radar (say light aircaft flying into Essendon) and the controler is unsure of your ID he/she will ask you to turn the aircraft. The second method is scramble a couple of fighters (Note 1). In fact its amazing no one scramble any fighters on MH370, inspite of it traversing at least 2 different military zones. A point I will make here in the tracking of MH370 by military radars, for the last part of the track its only ASSUMED that its MH370 as no fighters were scrambled to get a positive ID.
A third point on primary radar is that its not particularly accurate of longer distances, Note longer distances require VERY high powers, this is not to serious issue is extremely high power magnatrons are readily availible.
Note 1: This is regular done, in fact in countries like Britain, its usual to have at least two fighters on short time standby is its air spaces are regulary probed either deliberately or accidently.
From the analysis of the wreckage wash up from MH370, is certain that the aircaft has come done in the southern Indian ocean. Further analysis shows its almost certain that the aircraft hit the ocean at high speed.
Calls are being made that the electronic equipment to enable the aircraft to be indentified should not be able to be turned off. This has a number of issues. The first is that electrical problems are a common fault in todays aircraft. The reason it does not show is that the aircrew are trained to quickly isolate such problems before that become serious. One could over come this partly by taking much more care on the design and installation of wiring to such electronic devices. This would of course markedly increase the price of the aircraft.
Second issue is that even if one did something like that there would by nothing to stop the crew going down into the electronics bay and simple unpluging the device concerned.