My money would be on the fibre-glass honeycomb fairing failing first. As has been described by Mechanical Man (747 engineer), the fairing is screwed on. In the close-up photo, you can see the fairing at the front has failed (cracked or been pulled away from the screws) along the screw line. At the rear edge the screw holes are still there. However there is a bracket/strap still attached to the hull - lower centre. Is this used to attach the fairing in any way? (Perhaps mechanical man might confirm?) Is there a corresponding bracket on the upper half (where no metal exists now)? There is a scenario that the fairing came off due to wind pressure, and due to damage or failure of the leading edge screws. Once on the move, with the bottom bracket/strap already failed, the only retainer left would be this upper bracket ??? (if it exists) that, if it is like the lower one, seemingly is attached direct to the fuselage. (Maybe the fairing flailed around for some seconds) Coupled to a degree of corrosion at the same point, the force could be enough to initiate/propogate a crack, cause pressure failure and the rupture of the alu as seen.
