This is a quite technical article in a business journal but for those interested in the subject worth reading and you can skip some of the technical stuff and just read the conclusions. The whole article is here.
Unusual Option Market Activity and the Terrorist Attacks of September 11, 2001*
Allen M. Poteshman
University of Illinois at Urbana-Champaign
After September 11, 2001, there was a great deal of speculation that the terrorists or their associates had traded in the option market on advanced knowledge of the impending attacks. This paper generates systematic information about option market activity that can be used to assess the option trading that precedes any event of interest. Examination of the option trading leading up to September 11 reveals that there was an unusually high level of put buying. This finding is consistent with informed investors having traded options in advance of the attacks.