Since the advent of modern terrorism there has been a continuous evolution of the threat to aircraft by bombs. As officials have implemented increased security measures in response to prior attacks, creative bombmakers have found increasingly innovative methods to smuggle explosive devices onto aircraft. Bombmakers have hidden explosives in a wide variety of objects ranging from tea sets, radios and liquor bottles to toothpaste tubes, underwear and shoes. Because explosives come in a variety of forms that include powders, solids, liquids, gels and putties, the only real limit is the imagination of the bombmaker.
In many ways, this history of adaptive bombmaking is analogous to the continuous innovations in narcotics smuggling. This similarity highlights the fact that it is impossible to use technical screening measures to completely prevent explosive material from being brought on board an aircraft. Prison authorities have the latitude to engage in techniques extending to magnetometers and cavity searches to screen prisoners entering their facilities. And yet even they fail to stop all contraband from slipping through their security system. Less invasive air security checks cannot hope to prevent what stringent prison checks cannot.
But this does not mean that all airline passenger screenings are futile. At the very least, such measures prevent low-level threats from succeeding. The impossibility of a foolproof system, however, means that given enough persistence an innovative attacker eventually will get a device through the system. That next device might function better than the shoe bomb and the underwear bomb — cases in which disaster was only narrowly averted.
The Silver Lining
Al Qaeda in the Arabian Peninsula has long sought to attack the United States, but has not been able to send operatives to conduct such operations. Because of this, the organization has pursued a dual approach aimed at mounting a successful attack against the U.S. homeland. First, the group tries to inspire grassroots operatives to conduct attacks and then equip them to do so with easy-to-follow instructions. The group's publication of Inspire magazine is an example of this approach.
Second, the group has simultaneously sought to project its reach from its base in Yemen to the United States by launching attacks against U.S.-bound aircraft using concealed explosives — an underwear bomb and computer printer bomb.
Large numbers of militants have traveled to Syria to fight alongside rebel groups against the regime of Bashar al Assad. Many have joined jihadist groups such as the Islamic State and Jabhat al-Nusra. The sheer number of foreign fighters raises fears that some of these fighters could return to their home countries to conduct terrorist attacks. If Jabhat al-Nusra is indeed involved in this latest plot, it indicates that the group has not been able to use its foreign fighters to establish cells of highly trained terrorist operatives inside the United States. Currently, it too is limited to conducting remote attacks against the United States.