Really interesting article on the difficulties involved with explosive detection at airport security checkpoints.
Abstract: The mid-air bombing of a Somali passenger jet in February was a wake-up call for security agencies and those working in the field of explosive detection. It was also a reminder that terrorist groups from Yemen to Syria to East Africa continue to explore innovative ways to get bombs onto passenger jets by trying to beat detection systems or recruit insiders. The layered state-of-the-art detection systems that are now in place at most airports in the developed world make it very hard for terrorists to sneak bombs onto planes, but the international aviation sector remains vulnerable because many airports in the developing world either have not deployed these technologies or have not provided rigorous training for operators. Technologies and security measures will need to improve to stay one step ahead of innovative terrorists. Given the pattern of recent Islamic State attacks, there is a strong argument for extending state-of-the-art explosive detection systems beyond the aviation sector to locations such as sports arenas and music venues.
I disagree with his conclusions—the last sentence above—but the technical information on explosives detection technology is really interesting.