R. William Johnstone served on the 9/11 Commission, and wrote this book to build upon and supplement the Commission's work. In its pages, he explains the aviation security system failure on 9/11, uses that as a means for evaluating post-9/11 transportation security efforts, and proposes remedies to continued shortcomings. This book is based on information originally provided to the 9/11 Commission, augmented by unpublished reports and a wealth of other material that has come to light since the issuance of the Commission's own report in July 2004. Part One analyzes the aviation security system's history and institutions to explain why the system failed on 9/11. Part Two looks at what has been done in aviation and transportation security since 9/11, including the Commission's recommendations and the congressional response to them. Finally and most significantly, Part Three outlines a suggested approach for improving current U.S. transportation security.