[BigBobber]

Obviously, it would be easier and more certain for the terrorists plans to bring something onto the plane that looked like a bomb, but was not a bomb, thus would not be detected by screeners.

A real strap-on bomb and a fake strap-on bomb look the same to an airport screener. They were only doing a visual and metal search. Screeners had no way to detect explosives on passengers on 9-11. Therefore it was not any easier or more certain to smuggle a fake bomb as you suggest.

Both real and fake bombs entail the same risk of detection getting onto a plane. One gives you a huge advantage of completing a suicide mission (i.e. at least killing all the passengers and crew) and other does not. So why risk the mission to bring something on a plane that can only be used to scare people?

Since all the terrorist flights were incinerated, there may never be direct evidence of bombs on these flights. We do have these FACTS:

The passengers reported seeing the bomb on a terrorist.

The strap-on bomb is a MO often used by Islamist terrorists.

Significant debris was found miles from the main crash site.

The new information from the FBI. One of the terrorists told another terrorist (in Arabic) to "crash the plane".

[Pukka Puck]

"Both real and fake bombs entail the same risk of detection getting onto a plane."

You cannot be so stupid as to believe this.

[Pukka Puck]

"One of the terrorists told another terrorist (in Arabic) to "crash the plane"."

Yes, he said to crash the plane, he did not say to blow the plane up using the handy strap on bomb we have smuggled onto the plane at great risk for no good reason.