The next initial theory to join the list. The cockpit windscreen cracks & the co-pilot? at the controls not belted in? is sucked out. The Pilot? returning from a bio-break is unable to re-enter cockpit. The Plane takes an auto descent due to de-pressurisation.
I think the sound of the air rushing into the cockpit would exceed the noise of the pilot? knocking on the cockpit door.
How close to Gap - the Monte Carlo Rally route is the crash site?
I have relatives flying around Europe/ the Planet regularly, I certainly wonder where they are at times when unfortunate events like this happen.