Sky News' latest expert's hypothesis is that following a decompression, the pilots set the AP on a reciprocal course, and passed out after failing to put on their oxygen masks.
If that's the case, based on the expected flight distance and allowing for a bit of extra fuel, the aircraft could be down somewhere between Madagascar and Perth (Australia).
Is there any reason why pilots would fail to put on their oxygen masks? Could they fail?
Is there anywhere a decompression could occur that would take out the various communication systems?