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On 11 September 2001, Al-Qaeda used four hijacked civilian jet airliners in the US to kill nearly 3,000 people from 80 nations. This exposed a whole new degree of vulnerability in the global transport system. New security measures were introduced, initially for aviation but later for other forms of transport as well, including shipping, ports and cargo containers. Better security is vital when the risk of weapons of mass destruction reaching international terrorists is rising.
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Michael Richardson (2004) studied this question.
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