The would-be bomber Umar Farouk Abdulmutallab apparently ignited a plastic explosive with a syringe sewn into his underwear on Christmas as Northwest flight 253 prepared to land in Detroit. According to press accounts and the complaint filed against him by the U.S. Department of Justice, Abdulmutallab had secured on his body the explosive device, which contained PETN, or pentaerythritol tetranitrate—the same explosive chosen by the shoe bomber Richard Reid as well as various other terrorists since the early 20th century. The question is: could the device have been detected?

The technology answer is simple: Yes. So-called backscatter X-ray technology (devices that pick up the radiation bounced back by objects) generate a detailed image of any object on a person—as well as the person himself or herself—and reflect back a different image for, say, skin versus a concealed explosive. And other technologies—millimeter wave sensors, neutron bombardment, quadrupole resonance—can do everything from securely screening passengers without a pat-down to determining the precise chemical makeup of an object.

While Schipohl Airport in Amsterdam does have backscatter and millimeter wave devices, the airport does not routinely employ them on passengers as they are just for testing at this point. And Lagos Airport in Nigeria, where Abdulmutallab began his journey and grew up, does not have any of this technology, though it did meet U.S. Transportation Security Administration standards. It remains unclear what screening technology was specifically used on Abdulmutallab, though he likely passed through at least one metal detector while any luggage would have passed through a standard X-ray machine—neither of which necessarily would have picked up an explosive packet or syringe.

More advanced backscatter X-ray devices are routinely employed at the White House, among other high security areas, while millimeter wave sensors have debuted everywhere from London's Heathrow Airport to Baghdad's Green Zone.

But no amount of technology is foolproof. Devices must be precisely programmed to detect specific threats, and human ingenuity, whether in the service of drug smuggling or for less nefarious efforts, continues to evolve new ways to evade security measures. In fact, Abdulmutallab passed a routine security screening that involves an in-person interview and his fellow passengers have described him as "normal."

Ultimately, the best defense may be fighting unpredictable terrorist attempts with unpredictable, layered security screening. By evolving one set of procedures and employing a set array of technologies, security officials offer would-be terrorists something they absolutely require: the opportunity to plan. Adding the element of the unexpected to airport screening might be tough on travelers, but it also would keep malefactors guessing.

Image: Courtesy of TSA