CAPPS is also known (to the chronically
verbose) as the Computer Assisted Passenger Pre-screening System. CAPPS is the
FAA's solution to US-based airlines' claimed inability to maintain 100%
PPBM with reasonable efficiency.
Since the airlines can't guarantee that every bag onboard an aircraft has a corresponding passenger, the CAPPS system is used to identify high-risk travellers so that they can be scrutinized more closely, along with their bags. Usually this extra scrutiny takes the form of bag matching or screening with an Explosives Detection System (EDS). In addition to selecting travellers that fit a high-risk profile, the system also flags those for which there is insufficient information to make a firm decision, as well as a random percentage of passengers with checked baggage.
The system does not make use of information such as race, name, or sex when selecting passengers for additional security measures. Several studies have been undertaken by the US DOJ and DOT to confirm that CAPPS does not dispropotionally affect minority groups.
Currently, CAPPS is only used to screen passengers with checked baggage. Carry-on bags are still only subjected to the normal security procedures. New recommendations suggest expanding the system to cover all passengers, as well as increasing the pool of passengers flagged by the system. Look for big changes to the CAPPS system in the months ahead.