According to one unnamed senior al-Qaida associate, various ideas were floated by mujahadeen in Afghanistan, the commission said. The options included taking over a launcher and forcing Russian scientists to fire a nuclear missile at the United States, mounting mustard gas or cyanide attacks against Jewish areas in Iran or releasing poison gas into the air conditioning system of a targeted building.
http://www.nytimes.com/aponline/national/AP-Sept-11-Commission.html