Airports are facilities that wish to welcome and serve people who intend to use the airport and the airplanes that fly in and out of the airports for their intended purpose, i.e., safe and efficient arrival and departure in moving from one place to another. On the other hand, airports want to exclude from their facilities and airplanes those who intend to do harm to airport industry personnel and or airport patrons. The effectiveness of airport security depends on the airport having the resources, the commitment, the technology, and the procedures that can accurately distinguish in the most efficient manner possible those persons who pose a threat to the airport, its planes, and its patrons. These features of effective airport security also apply to the security features and requirements of border control for nations as they seek to admit those who will obey the nation's laws and behave responsibly within its borders while excluding those who are at risk of causing harm. The difficulty is in distinguishing dangerous from nondangerous users of airports and airplanes. This is typically done by obtaining reliable information on those who seek to use the airport, which in turn depends on the ability of security officials to obtain and/or recognize accurate patron information as to identity, background, and possible risk of doing harm to others while using the airways. Attempts to correctly assess the correct identity and risk of a passenger can involve screening prior to the person's arrival at the airport, procedures at the airport prior to entering a plane, and surveillance after the admitted passenger enters the plane. 2 tables, 1 figure, and 31 references