Flying after 9/11

Hi All,
Question 3 on the HW asks about flying after 9/11.  While the gasoline question is somewhat uncertain because of the increased supply of oil after 9/11 and the increase in demand from US military forces for its actions in Afghanistan, the number of people flying after 9/11 dropped significantly.  For future reference, please see www.bts.gov and this attached PDF from 2005.

http://www.bts.gov/publications/special_reports_and_issue_briefs/issue_briefs/number_13/pdf/entire.pdf