You are making assumptions that there is incriminating evidence and terrorist voices on the black box. It should be noted that there is actually two boxes on commercial jets, I believe an orange box and a black box. What is on either of those , if intact, is much more likely to show us what happened via the plane's maneuvers, rather than any middle eastern swearing over a radio. The FAA will analyze this flight data and , I suspect, show that perhaps during the struggle to subdue the pilot and copilot, that the plane with either intentionally or unintentionally put into a dangerous maneuver that was unable to be recovered. Either way, the most important thing is that they were not allowed, by the grace of the powers that be, to take many more innocent lives....which no doubt would have happened should they have reached their "target", whatever it may have been.