Daniel Ellsberg, who leaked the classified Pentagon Papers to the New York Times in 1971, supports the claims of 9/11 denialists like University of Wisconsin Lecturer Kevin Barrett (see here and here). The following is quoted from a July 14, 2006 interview with Ellsberg:
Interviewer Jack Blood: "I’m gonna take a risk here in asking you this Daniel, in all due respect, have you had a chance to look at this information coming from America’s leading scholars, business’, engineers, etc. who have taken a look now at 9-11 and are now not only questioning what might have happened on 9-11, but really being very direct…."
Daniel Ellsberg: "I have looked at a lot of that and I tell ya, without going into it all, which would take a lot of time, I find some of it very implausible and other parts of it, quite solid. There is no question in my mind, that there is enough evidence to justify a very comprehensive and hard hitting investigation of the kind we have not seen. With subpoenas, general questioning of people, releasing a lot of documents. There’s no question that very serious questions have been raised about how much they knew before hand and how much involvement there may have been. Is the administration capable, humanly, psychologically, of engineering such a provocation? Yes. I would say that."