This is a subject the "Independent" 9/11 Commission has dealt with, but it remains to be seen how effectively, as noted by Tom Flocco:
9-11 Commission Testimony Too Hot To Be Under Oathhttp://www.tomflocco.com/9-11_commission_Testimony_too_hot.htm'...
Then Vice-Chairman Lee Hamilton entered the fray, asking Arnold when President Bush gave the order to shoot down airliners assumed to be hijacked, and why that exact time of the shoot-down order was not entered into the official NORAD 9/11 timeline, presented and discussed in front of the Commission just minutes prior to Arnold's questioning -- one that NORAD admitted to having reconstructed well after the fact, using some estimated times.Arnold advised that at one time during the morning of September 11, some “21 airliners were called ‘hijacked.’ ” But Vice-Chairman Hamilton pressed the General for an answer to his original question --one which also has critical time-line implications.
Arnold answered Hamilton, offering more incredible, but un-sworn testimony: “I am sure that information is available,” Congressman Hamilton, adding “I appreciate your question.” Everyone in the hearing room seemed stunned at his answer.At that point, Kean and Hamilton were becoming perturbed with Arnold, asking that he “provide for the record, the chain of command for the shoot-down order on September 11.”
At that moment, reporters, victim family members, and others began quietly looking at one another -- with soft, almost inaudible murmurs bouncing around the hearing room....'