Regarding the missle theory...
According to a friend of a friend of my uncles brother (actually a NTSB investigator)
the section of a 747 with the highest IR sig is not the 4 Pratts at climb power but the air conditioning packs under the CWT.
So any IR seeking missle would hit there and not one of the engines.
When asked to clarify, he told me that the exhausts are washed with cool fan discharge and therefore have a lower IR sig therefore hiding the hotter internal parts of the engine to a IR seeking missle.
Well he had me convinced.
: DD :