From the above link:
Plus indications - now from London - that signals showing the plane was still in the air up to five hours after last contact. So maybe not entirely fanciful to consider hijack after all.
A suicide hijack ? Otherwise where did they land and why haven't they made any demands ?
Perhaps they flew around for a while and just ran out of fuel and crashed, but you would think that hijackers would make some sort of demands over the radio.