I presume that the “black box” is located somewhere in the plane that is likely quite inaccessible to the crew and/or terrorists that may wish to disable it. It’s a sealed box, and I would presume that the crew would not have the tools to open it and that it is unlikely to have a simple “on/off” switch with which to turn it off.

But… COULD it have been diaabled? Why have no “pings” been picked up as yet?