"Y'know, all those complaining about conspiracy theories believe that a small group of very recent terrorists based in Iraq/Afghanistan successfully conspired to setal several jetliners and plough them into buildings, possibly killing tens of thousands."
And what's irksome to me about "Truthers" is their inability to draw a distinction between the two scenarios. You disingenuously argue that somehow this terror plot is equally as implausible as the "Truther" hypothesis, when in reality the two explanations are hugely different.
The terror plot explanation has very few points of failure. All the hijackers had to do was hijack planes, and fly them into their targets. That's it. And one of them failed to do even that, crashing the plane into a field.
They needed to find 4 flights departing about the same time, know enough about piloting to steer a jet already in flight, and smuggle weapons on the plane with which to subdue the crew members. They took advantage of our policies on hijackings, which were written for the scenario where a hijacker has demands to be met and isn't looking to die a martyr.
Now, the "Truther" explanation?
It requires two massive structures to somehow be outfitted with sufficient explosives to be brought down, with not one of the thousands of people in the building noticing them, which would be difficult given the open floor plan of the WTC.
It requires all the people who outfitted the structures with these explosives to keep mum about it.
It requires the planes hit the buildings in very precise locations, otherwise you'd have a problem with severed wires from the detonators to the explosives.
It requires some way of controlling where the fires happen, lest the explosives be triggered at the wrong time, or out of sequence.
Occam's Razor is useful.