I imagine some guy sitting in a darkened basement somewhere, his face lit only by the harsh glow of his computer's LED screen, catching the smoke coming out of his ears as he tries to reconcile two contradictory ideas.
Inded:
Boeing is not in-on-it and had no involvement in it but at the same time they noticed that there is something strange about the supposed Boeing 767 that flew into the tower and knowing that it could get them into someone's bad books all engineering staff who bring this up are told not to talk about it again for the rest of their lives.
Yeah!
People know that something is not what it seems but all of them stay silent for ten years.
People know that it was not a standard Boeing 767 of the type used for flight 175 but stay silent for ten years.
I hilite "people" because saying that "Boeing" knows or is/isn't involved is a way of depersonalizing this. "Boeing" consists of people. Lots of them and a good percentage of them would be knowledgable in the design of aircraft and several dozen at least in the specifics of a 767 yet all of these
people have stayed silent.
Of course they may have been bought off or threatened by someone, cowed into silence. That would of course mean that they positivley know that something was amiss in the evnts of 9/11.
Engineer: There is something odd about that supposed 767. I'd like to investigate this a little more and perhaps exhonerate Boeing from being the conveyer of death on 9/11.
Supervisor: Hmmm, you could be right.
Upper management: Cease and desist all investigation in this matter. Here's $100,000 to never mention it again. If you do mention it again to anyone, either of you, then you or a loved one might suffer a fatal accident.
Engineer and Supervisor (to themselves): OMG there really is something to the conspiracy theories 'out there'.