What I said in my previous was that the debris field, even at six miles in length, was far too small for the aircraft to have broken up at cruise altitude as would have been the case if it were shot down.
The aircraft was clearly out of control, probably due to a struggle in the flight deck. There is a possibility that the hijackers did have a bomb managed to detonate it which would explain why it now seems that the debris field was bigger than initially thought.