According to TSA, the majority of air carrier passengers present a low risk to aviation security, but until recently, with the exception of passengers matched to watchlists, TSA has used the same security screening procedures for passengers without regard for the risk passengers posed. TSA, through the Secure Flight system, utilizes watchlists derived from the Terrorist Screening Database—the U.S. government’s consolidated watchlist of known or suspected terrorists—and other sources to identify potentially high-risk passengers. For example, the No Fly List contains information on individuals who are prohibited from boarding an aircraft, and the Selectee List contains information on individuals who must undergo additional security screening before being permitted to board an aircraft. As part of TSA PreTM, TSA conducts terrorism related checks using lists derived from the database as a part of the security threat assessment process. In 2011, TSA began to explore the benefits of using risk-based, intelligence-driven security screening procedures that would allow TSA to learn more about passengers prior to travel because, according to TSA, it can better assess passenger risk when it knows more about passengers. In addition, TSA worked to develop procedures to ensure screening resources are focused on passengers determined to be high risk and passengers about whom TSA has less information while expediting the screening of passengers TSA has assessed as being lower risk based on information it has on such passengers. Using this risk-based approach, TSA began to identify and define lower risk passenger populations or “known travelers”—that is, those who have volunteered personal information to TSA so that TSA can confirm these known travelers are lower risk. When TSA began offering expedited airport screening in the summer of 2011, TSA initially provided such screenings in standard lanes to passengers aged 12 and younger, and subsequently extended expedited screening to certain flight crew members and then to passengers aged 75 and older. In October 2011, TSA began to expand the concept of expedited airport screening to more of the flying public by piloting the TSA PreTM program. This pilot program allowed certain frequent fliers of two air carriers to experience expedited screening at four airports. These frequent fliers became eligible for screening in dedicated expedited screening lanes, which became known as TSA PreTM lanes, because they had opted into the TSA PreTM program through the air carrier with which they had attained frequent flier status. TSA also allowed certain members of the U.S. Customs and Border Protection’s (CBP) Trusted Traveler programs to experience expedited screening as part of the TSA PreTM pilot. TSA provided expedited screening in dedicated screening lanes to these frequent fliers and CBP’s Trusted Travelers during the TSA PreTM pilot program because TSA had information about these passengers, and TSA used this information to determine that passengers in these groups were lower risk. When traveling on one of the air carriers and departing from one of the airports participating in the pilot, these passengers were eligible to be screened in dedicated TSA PreTM screening lanes where the passengers were not required to remove their shoes; divest light outerwear, jackets, and belts; or remove liquids, gels, and laptops from carry-on baggage. After the pilot concluded, in February 2012, and transitioned into a formal program, TSA began to add additional air carriers and passenger groups to the TSA PreTM program. For an air carrier to participate in TSA PreTM, the air carrier must have the technological capability to send the necessary passenger information to Secure Flight for vetting against federal government watchlists, and print the low-risk designation in the encrypted boarding pass bar code and the TSA PreTM designation on the boarding pass. As each air carrier joined TSA PreTM, the carrier’s frequent fliers became eligible to opt in for expedited screening only when traveling on that air carrier. Since October 2011, TSA further expanded the known traveler populations eligible for expedited screening. After TSA piloted TSA PreTM with certain passengers who are frequent fliers and members of CBP’s Trusted Traveler programs, TSA established separate TSA PreTM lists for additional low-risk passenger populations, including members of the U.S. armed forces, Congressional Medal of Honor Society Members, members of the Homeland Security Advisory Council, and Members of Congress, among others. In addition to TSA PreTM lists sponsored by other agencies or entities, TSA created its own TSA PreTM list composed of individuals who apply to be preapproved as low-risk travelers through the TSA PreTM Application Program, an initiative launched in December 2013. To apply, individuals must visit an enrollment center where they provide biographic information (i.e., name, date of birth, and address), valid identity and citizenship documentation, and fingerprints to undergo a TSA Security Threat Assessment. TSA leveraged existing federal capabilities to both enroll and conduct threat assessments for program applicants using enrollment centers previously established for the Transportation Worker Identification Credential Program, and existing transportation vetting systems to conduct applicant threat assessments. Applicants must be U.S. citizens, U.S. nationals or lawful permanent residents, and cannot have been convicted of certain crimes. As of April 2014, there were about 5.6 million individuals who, through TSA PreTM lists, were eligible for expedited screening. Figure 1 shows the populations for each TSA PreTM list. In addition to passengers who are included on one of the TSA PreTM lists, in October 2013, TSA began implementing the TSA PreTM Risk Assessment program, which evaluates passenger risk using data available to TSA to determine a certain likelihood that passengers will be designated as eligible to receive expedited screening through TSA PreTM. According to TSA officials, in February 2013, TSA established a policy to notify passengers of their eligibility for expedited screening using the air carrier reservation systems in order to improve passenger movement through airports for TSA PreTM eligible passengers. For every passenger, TSA uses the Secure Flight system to automatically match passenger information collected by the air carriers against the various watchlists (e.g., the No Fly and Selectee Lists) up to 72 hours before passengers’ scheduled air travel. After checking for matches to the watchlists, Secure Flight directs the air carrier to mark a passenger’s boarding pass for enhanced screening or expedited screening, or to identify a passenger as being prohibited from boarding an aircraft, or to identify a passenger for standard screening.TSA uses a similar process to identify passengers who are eligible for expedited screening at the airport by using the same information provided by the air carriers to the Secure Flight system to match against lists of individuals who have been designated as low risk. TSA informs passengers of this eligibility by directing the air carriers to mark the boarding pass with the TSA PreTM designation. Figure 2 shows examples of boarding passes with the TSA PreTM designation. At airports, the mechanism TSA uses to screen passengers who have the TSA PreTM designation on their boarding pass depends on the configuration of the airport. At some airports, TSA has dedicated TSA PreTM expedited screening lanes where passengers with the TSA PreTM designation on their boarding passes are not required to divest shoes, light outerwear, laptops, liquids, and gels. Because TSA PreTM expedited screening is voluntary, a passenger designated as eligible for TSA PreTM expedited screening may choose not to use a TSA PreTM dedicated screening lane. Also, some airports do not have dedicated TSA PreTM expedited screening lanes either because of space restrictions that preclude the airport from installing a dedicated screening lane in a security checkpoint or because the number of passengers with the TSA PreTM boarding pass designations is low and therefore does not warrant a separate dedicated lane. According to TSA officials, at these airports, passengers with a TSA PreTM boarding pass can still experience expedited screening of “their persons” (i.e., passengers are not required to divest shoes, light jackets, and belts) and use a walk through metal detector in the standard screening lane; however, they must divest their liquids, gels, and laptops from baggage because the screening process used in the standard screening lanes should result in the transportation security officer (TSO) identifying these items and searching the baggage—slowing throughput in the standard screening lane—if these items are not removed. For airports at which there are dedicated screening lanes, security checkpoints may not consistently have a volume of TSA PreTM passengers that warrants operating such lanes because the TSO working in the lanes would be underutilized. Also, an underutilized expedited screening lane can result in longer wait times in standard screening lanes because airports that offer expedited screening in dedicated screening lanes generally do so at the expense of standard screening lane availability, according to airport and TSA officials. To ensure the utility of expedited screening lanes for non-TSA PreTM passengers, TSA implemented the Managed Inclusion process in November 2012. The Managed Inclusion process involves using real-time threat assessment methods, including randomization procedures and behavior detection officers (BDO), as well as either canine teams or explosives trace detection (ETD) devices to screen non-TSA PreTM passengers in lanes that are otherwise dedicated to TSA PreTM passengers.