All males have a body cavity. Females have two body cavities. In prisons, these body cavities are habitually used to smuggle drugs and improvised weapons past body searches, including complete nudity strip searches.

Given the power of widely available explosives, the amount that can be carried inside a body cavity—let alone two—is sufficient to destroy ordinary pressurized airliners at normal flight altitudes. That makes "pat downs," or indeed any form of physical inspection that is remotely feasible...