CAPPS II: the foundation of aviation security?

A new computer system is being developed to classify U.S. air travelers by the degree of terrorist threat they might pose. Reports indicate that the system--called CAPPS II--would use large amounts of information about each passenger, perhaps including such personal details as his or her magazine-subscription behavior. We argue that what is publicly known about CAPPS II raises questions about how substantially the system would improve aviation security. We discuss conditions under which CAPPS II could yield safety benefits, but suggest that it might be more prudent to view the system as one component of future security arrangements rather than the centerpiece of these arrangements.