When most people think of anti-terrorism and air security, they primarily think of a September 11th situation where terrorists target a passenger plane, hijack it, and proceed to use it as a weapon. Alternatively, they may think of a hostage situation where a plane is hijacked, and the passengers are held hostage while a series of demands are made. Those, however, are not the only threats from air travel. Air cargo is, itself, topic of concern for the security community as they too could either be detonated in the air or hijacked and used as mass casualty weapons. In fact, some of the concern for cargo security exists because of the enhanced screening and passenger vetting that has occurred on travel into and within the United States since the September 11th attacks. The threat from cargo exists both on planes carrying only cargo and amongst cargo that travels with passengers; however, it is believed that cargo-only traffic is considered less of a threat. The primary threat posed by cargo-only traffic is hijackings; whereas, explosives are a large concern for cargo traveling with passengers.