The promoters of nude body scanners have used one argument that they consider to be bullet-proof. It is all about saving lives, they assure us. The news reports that accompanied the announcement of their sudden and universal installation reported passengers accepting the scanners because what they gave up in modesty they got back in added security.
Or did they?
What exactly is the gain in security as a result of mandating these legal obscenities? How big is the current risk and how much will it be reduced by the new measures?
These are the questions that have not been explored. And here is the big news. For even the best case analysis shows that the gain is so small as to be totally insignificant.
Available data indicates that flying is a very safe mode of travel and the further increase in safety with the new measures will be very marginal. Based on historic official data currently the probability of a passenger dying in an air carrier accident is 1 out of 2,067,000 (much smaller than the one for motor vehicles, which is 1 out of 7,700). With the drastic measures now being implemented, in the best case scenario, this will only be reduced to 1 out of 2,271,428.
The expected improvement can be calculated by looking at the historic data for causes of aircraft fatal accidents. Available records for the past sixty years show that sabotage has been a very small and decreasing contributor to the overall aircraft fatal accident probability. Planecrashinfo.com analyzed data for all aircraft fatal incidents that occurred from 1950-2008. Only 9% of these were caused by sabotage, which includes use of explosives, shoot downs, and hijackings. In other words 91% of all commercial aircraft accidents causing fatalities were caused by other factors. Of these 50% were caused by pilot error, 22% by mechanical failure and 12% by weather.  The contribution to fatal accidents by sabotage was the highest in the 1980s and has been decreasing ever since. It stood at the 58-year average of 9% for the 2000s.
It does not take a genius to figure out that much bigger gains in saving lives can be made by addressing the factors that contribute to the 91% of the problem. That there is room for improvement there is indicated by a six-month USA TODAY investigation that found that during the past six years, millions of passengers have been on at least 65,000 U.S. airline flights that shouldn't have taken off because planes weren't properly maintained. According to the report, the Federal Aviation Administration (FAA), which oversees airlines, levied $28.2 million in fines and proposed fines against 25 U.S. passenger airlines for maintenance violations that occurred during the past six years. This only represents a small fraction of the actual problem, because "about 90% of maintenance violations don't result in fines but warning letters or other reprimands by the FAA."
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