X-ray machines that screen airline passengers' shoes cannot detect explosives, according to a Homeland Security Department report on aviation screening.
The headline is inaccurate. The Rapiscan x-ray machines deployed at most US airports can, in fact, allow screeners to find explosives. Screeners are trained to use x-ray machines to detect the components of Improvised Explosive Devices (IEDs): timing devices, detonators, switches, and the main charge - the explosive.
I haven't seen the report, which is most likely classified and should earn the leaker a trip to Leavenworth, but from what AP has written, it most likely was pointing out that the small amount of explosive in a shoe bomb would be difficult to detect. True. That's what Explosive Trace Detection (ETD) equipment is for. But what's a good indicator to determine which shoes might deserve to be tested by the ETD? Anomalies in the x-ray image of the shoe.
Journalists are usually generalists. They should check with experts before publishing inflammatory stories about technical subjects.