Findings from the report, obtained by The Associated Press, did not stop the Transportation Security Administration from announcing Sunday that all airline passengers must remove their shoes and run them through X-ray machines before boarding commercial aircraft. (...)Link (thanks, rich mogull)
In its April 2005 report, "Systems Engineering Study of Civil Aviation Security – Phase I," the Homeland Security Department concluded that images on X-ray machines don't provide the information necessary to detect explosives. Machines used at most airports to scan hand-held luggage, purses, briefcases and shoes have not been upgraded to detect explosives since the report was issued.
Reader comment: Dr. Paul J. Camp says,
In World War II, the OSS used to send spies and saboteurs into occupied Europe with, among other things, knives concealed in the soles of their shoes. I doubt the trick has been forgotten, and if it is ceramic rather than metal, the knife wouldn't set off the metal detectors. You can easily obtain a ceramic knife blade at any of your higher end cooking-as-a-fashion-statement stores. Just because X-rays don't catch the terrorist-du-jour doesn't mean they are useless. Now that I've written this, the NSA will probably be listening in on all my future phone calls.