While I do not put it past Iraq or North Korea as possibly having a crude or "dirty" nuke on hand, I doubt the Terrorists have one as it would have been used by now. As a matter of question; why would they have taken the time to train 20 or so men to fly an aircraft into a building when they could have simply sit in the harbor and rowed a boat ashore placing their 'device' next to buildings and making most of the lower tip of Manhattan a garbage dump?
I am with you, I think they do not have one, but will do anything to try and get one.
Why would nukes be more likely after 9/11 than before???
Why would they be interested in crop dusters for unwieldy bioterror, and not small cargo-carrying type planes for a nuke delivery??