there's a different between building planes and keeping it a secret. i honestly don't think many people would have a problem keeping the construction of a plane under wraps. but the general thesis is, one of the thousanRAB (at least) people who would have had to been involved in 9/11 would have said something to the effect of, "hey, the goverment orchestrated the murder of 3,000 of its own citizens for political purposes - i can't keep this a secret."