" "The pilots carried out a complex & carefully planned, homicidal suicide" looks like a bigger assumption than hijacking by a government to me. "
On the rather bold assumption that the technology exists to simply take over a 300-something seat passenger jet at will, I'm still rather lacking the motive? That they'd kill this many people from a friendly nation just to test the technology? Don't you think that they'd have done that with unmanned airliner a few times first (technology to remote control passenger jets does exist but you need to install a lot of equipment in the jet you want to fly by remore first). It all seems way too farfetched and way too conspiratorial without any real motive other than 'just because you can'. Were there any USAF E-3 Sentries operating in the area that night?
Whereas the homicidal suicide of a suicidal pilot on a passenger jet has happened at least 3 times to my knowledge.
Of the two choices, the one that has already occurred multiple times and doesn't rely on, frankly, motiveless, ficticious hacking technology would be the one I'd go for, so Occam's Razor would dictate that the suicide theory is the simplest, cheapest, least technically complex and most likely to succeed option.