They did in the 1993 WTC bombing. The FBI informant initiated the plot as first using pipe bombs for synagogues. Then later it evolved and he built a real bom

They did in the 1993 WTC bombing. The FBI informant initiated the plot as first using pipe bombs for synagogues. Then later it evolved and he built a real bomb under the supervision and direction of the FBI and the District Attorney. The informant wanted more money and eventually the FBI lost confidence in him and cut him loose. Approximately 6-months later the bomb exploded. Afterwards, he was rehired, paid a million dollars and used a fake bomb to catch other would-be terrorists. The evidence of this is the hours of audiotapes he recorded which was covered in several NYTimes articles. The odd thing is the plot started before Ramzi Yousef entered the country. And the two Iraqi brothers, where Yousef first went, and the lady associated with them, were never caught. I don't think it was a malicious conspiracy but it was gross negligence and there is indication that the FBI wanted to catch the terrorists in the act to teach them a lesson. Even worse is that KSM is Yousef's uncle and there were several neo-con writers who cast doubt on Yousef's true identity whilst trying to link him to Iraq.