As part of its responsibilities for civil aviation security, TSA enforces law and regulations requiring that passengers be screened to ensure that potential weapons, explosives, and incendiaries are not carried into an airport sterile area or on board a passenger aircraft. To provide the general public with guidance on the types of property TSA policy prohibits from being brought into airport sterile areas and on board aircraft, TSA publishes, and on occasion has updated, an interpretive rule in the Federal Register--known as the PIL--that, among other things, lists items prohibited from being carried on a passenger's person or in the passenger's accessible property into airport sterile areas and into the cabins of passenger aircraft. TSA also maintains a current list of prohibited items on its public website. The list is not intended to be exhaustive, and TSOs may exercise discretion, informed by the categories and examples included in the PIL and their standard operating procedures, to prohibit an individual from carrying an item through the checkpoint if in the screener's determination the item could pose a threat to transportation (i.e., whether it is or could be a weapon, explosive, or incendiary) regardless of whether it is or is not on the PIL. TSA has divided prohibited items into nine categories. Table 1 provides a description of the items included in the nine categories. Individuals are prohibited from carrying these items into an airport sterile area or on board an aircraft either in their carry-on bags or on their person. At passenger screening checkpoints, TSOs inspect individuals and property as part of the passenger screening process to deter and prevent the carriage of any unauthorized explosive, incendiary, weapon, or other items included on the PIL into the sterile area or on board an aircraft.shown in figure 1, TSOs use the following methods, among others, to screen passengers: X-ray screening of property, Advanced imaging technology scanners (often referred to by the public as body scanners) or walk-through metal detector screening of individuals, pat-down screening of individuals, physical search of property, trace detection for explosives, and behavioral observation. TSA has developed checkpoint screening standard operating procedures that establish the process and standards by which TSOs are to screen passengers and their carry-on items at the screening checkpoint. According to TSA standard operating procedures, passengers may be screened through the use of a walk-through metal detector, advanced imaging technology scanner, or a pat-down. Passengers are also generally required to divest their property, including the removal of shoes and outer garments, and empty their pockets. During this screening process, TSOs look for any prohibited or dangerous items on a passenger or among the passenger's property. Ordinarily, passenger screening at the checkpoint begins when the individual divests and places his or her accessible property on the X-ray conveyor belt or hands such property to a TSO. A TSO then reviews images of the property running through the X-ray machine and looks for signs of prohibited items. The passengers themselves are typically screened via a walk-through metal detector or an advanced imaging technology scanner, and passengers have the option to request screening by a pat-down if they do not wish to be screened via the advanced imaging technology scanner. TSA uses additional screening techniques on a random basis to provide an additional layer of security. These additional screening techniques, referred to as an Unpredictable Screening Process, are prompted automatically by the walk-through metal detector, which picks out a certain percentage of passengers at random to be selected for additional screening. For example, TSA uses explosives trace detection (ETD) to swab the hands or property of passengers on a random basis to screen for explosives. According to TSA officials, because of statutory and other considerations, TSA has revised the PIL six times since its inception in February 2003 (see table 2). In general, TSA modifies the PIL as necessary when circumstances prompt the agency to revise the items listed as prohibited from being carried into an airport sterile area or on board an aircraft. For example, in 2005, TSA modified the PIL in response to a statutory requirement to prohibit passengers from carrying any type of lighter on their person or in their accessible property on board aircraft. Later that year, TSA also modified the PIL to allow passengers with ostomates to carry small ostomy scissors with them onto aircraft because the agency had heard from persons with ostomies that they avoid flying, in part, because they are not allowed to carry the scissors they need onto the aircraft. In 2006, TSA further modified its policy with respect to permitted and prohibited items in response to a specific terrorist threat by initially prohibiting the carriage of liquids, gels, and aerosols on board an aircraft, and subsequently permitting passengers to carry limited amounts of liquids, gels, and aerosols on board an aircraft in a manner prescribed by the agency. See TSA Security Directive 1544-14-02 (Feb. 6, 2014) and TSA Emergency Amendment 1546-14-01 (Feb. 6, 2014) (imposing additional security requirements on U.S. and foreign air carrier operations, respectively, to and from the Russian Federation). The security directive and emergency amendment did permit the carriage of medication in liquid, gel, or aerosol form. such measures are carried out, TSA generally accomplishes this by issuing security directives and emergency amendments and, as circumstances permit, in coordination and consultation with host governments, the International Civil Aviation Organization (ICAO), and other affected parties. TSA officials told us that when evaluating whether or not to change the PIL, they generally consider the following four factors: (1) the security risks posed by each item on the current PIL or potential item to be added, (2) opportunities a potential change may have to improving checkpoint screening and passenger experience, (3) harmonization with international aviation security standards and recommended practices published by ICAO, and (4) stakeholder perspectives on the change. For example, as part of a broader set of potential changes related to adopting a risk-based security approach to passenger screening, TSA formed a working group in 2011 to conduct a risk-based review of the PIL; assessed the individual risk posed by each PIL item; and then considered how removing a particular item, or set of items would present opportunities, constraints, and challenges for TSA security operations at the checkpoint. TSA officials stated they then considered how any changes would affect TSA personnel costs and passenger experience such as likely screening throughput time if TSA personnel no longer had to screen for particular items. TSA then evaluated how interested parties such as Congress, airlines, and flight attendants would respond to permitting particular items on board an aircraft. TSA also considered ICAO guidance on prohibited items and took into account whether any changes it made to the PIL would further align TSA's guidelines for prohibiting items with ICAO standards and recommended practices. TSA officials told us that TSA does not have policies that require a specific process to be followed or a specific set of criteria to be used when evaluating potential modifications to the PIL, since the circumstances for each potential PIL change are unique. Officials stated the steps they take when considering a modification often vary depending on the nature of the proposed revision. In its 2011 review of the PIL, TSA's working group addressed these factors as follows: Impacts on security risk: The working group evaluated the risk to transportation security presented by each prohibited item by assessing the likelihood of an adversary successfully using the item to achieve different terrorist objectives. TSA assigned risk ratings of high, medium, low, or none to each item on the PIL for each terrorist objective. TSA assessed the levels of risk posed by small knives for each terrorist objective. Impacts on screening operations: The working group also considered how the removal of small knives would affect checkpoint screening operations. For example, TSA estimated, using historical data prior to 2009, that approximately half of all nonfirearm, nonincendiary voluntarily abandoned property (VAP) left behind at the checkpoint consisted of small knives with blades shorter than 2.36 inches. TSA concluded that TSOs spent a disproportionate amount of their time searching for these items. TSA reasoned that removing small knives from the PIL would have a positive impact on screening operations since TSOs would no longer have to detect and deal with small knives at the checkpoint, reducing direct and indirect personnel costs, increasing passenger throughput, and reducing distractions to TSOs. TSA also concluded that not requiring TSOs to screen for small knives would in turn improve their ability to screen for higher-threat items, such as IEDs, and thus reduce risk overall. For example, the TSA risk assessment cited a research study focused on how success rates for screening items vary based on what screeners look for. TSA cited the study in support of its assertion that TSOs would be more successful identifying IEDs if they did not have to screen for small knives. Harmonization with international standards and guidance: TSA also considered the harmonization of the PIL with ICAO standards and recommended practices. TSA concluded that making certain changes to the PIL, such as removing small knives, could better harmonize its policies with ICAO guidance. Specifically, ICAO guidance provides that member states should consider prohibiting knives with blades of more than 6 centimeters (approximately 2.36 inches) from being carried on board aircraft. TSA concluded that there would be operational and policy benefits from harmonizing the PIL with ICAO guidance because greater harmony among the various countries promotes greater cooperation on all security issues. Further, TSA asserted that inconsistencies between the PIL and the ICAO guidance could create confusion for passengers when items were allowed onto aircraft in one country, but prohibited in another. Stakeholder perspectives: The TSA working group also noted the need to coordinate with stakeholders on some of the options for modifying the PIL, as these options were likely to cause concern among some of these groups, if implemented. For example, for the working group's proposed recommendation to remove small knives from the PIL, TSA officials noted past concerns from stakeholders over the prospect of allowing small knives or other items on board aircraft and stated that coordination and collaboration with key stakeholders would be a critical success factor for implementation. They also noted that stakeholder support would be greatly enhanced by a unified approach to communicating to stakeholder groups that TSA planned to shift its resource focus from finding small knives to other efforts that would result in better security. Although TSA recognized that allowing small knives on planes would raise the potential risk of other terrorist aircraft scenarios, TSA concluded the change would not raise the overall risk of catastrophic aircraft destruction. However, rather than make an immediate decision about changing the PIL, TSA elected to suspend working group activities and delay making any decisions while it focused greater attention and TSA resources on other emerging risk-based security initiatives, such as the Known Crewmember and expedited passenger screening programs. TSA resumed working group evaluations of the PIL in July 2012. As previously discussed, TSA used its risk assessment to conclude that overall risk to aviation security would be lowered by allowing small knives onto aircraft because security screeners would be able to better focus on identifying higher-risk items, such as IEDs. However, TSA did not conduct sufficient analysis to show that removing small knives would ultimately reduce risk and improve checkpoint screening. TSA's reasoning for its decision to remove small knives from the PIL was to further align the PIL with ICAO guidance on prohibited items, decrease time spent rescreening or searching bags for these items, and better enable its TSOs to focus more attention on higher-threat items, such as IEDs, thereby potentially increasing security. DHS guidance for managing and assessing risk states that risk assessments should evaluate all the In its risk assessment, risk scenarios considered by the assessment.TSA assessed the risk posed by small knives for each terrorist objective; however, it did not complete data collection or an evaluation to determine whether TSOs would actually be better able to identify high-risk items, such as IEDs, if they were not looking for small knives. Furthermore, the research cited by TSA did not evaluate a situation where screeners had to differentiate between knives with blades greater or less than 2.36 inches in length, as proposed by TSA. Without conducting a more valid evaluation of the actual proposed change, TSA could not sufficiently evaluate whether the added risk of allowing small knives onto aircraft would be offset by a reduction in risk achieved through improved screening for IEDs. Such an analysis would have allowed TSA to actually measure whether airport screeners would be better able to identify explosives if they no longer had to screen for small knives, and better determine whether the added risk of allowing small knives onto aircraft would be offset by potential efficiencies in screening for explosives. Moreover, 25 of 35 TSOs (including supervisory TSOs) and 8 of the 10 Transportation Security Managers we interviewed during visits to six airports did not agree that allowing small knives on planes would have helped them better screen for IEDs, as TSA concluded in its risk assessment. Four TSOs and 1 supervisory TSO we interviewed noted that the exact size of a knife is difficult to ascertain on an X-ray. Therefore, these 4 TSOs and the supervisor believed they would have to open bags in many instances and physically measure the knife to make sure it conformed to TSA's definition of a permissible knife, which, according to TSA's definition, was a nonfixed blade less than 2.36 inches and not exceeding a 0.5 inch in width with no locking mechanism, and no molded grip or nonslip handle. TSA officials told us that the training provided to TSOs specified that each TSO was expected to use his or her judgment in determining, based on the X-ray image, whether a knife was permissible or not. We previously recommended in 2007 that TSA strengthen its evaluation of proposed modifications to the PIL and other checkpoint screening procedures to better justify its decisions. Specifically, in April 2007, we found that TSA did not conduct the necessary analysis to support its 2005 decision to remove small scissors (4 inches or less) and certain tools (7 inches or less) from the PIL. As with TSA's more recent rationale for removing small knives from the PIL, TSA stated that the reason for its decision to remove small scissors and tools was to shift TSO focus from items considered by TSA to pose a low threat to items considered to pose a high threat, such as IEDs, as well as to better allocate TSA resources to implement other security measures that target IEDs. However, we found that TSA did not conduct the necessary analysis to determine the extent to which removing small scissors and tools from the PIL could improve TSO performance in detecting higher-threat items, nor did TSA analyze other relevant factors such as the amount of time taken to search for small scissors and tools and the number of TSOs conducting these searches. As a result, we recommended that TSA, when operationally testing proposed modifications to its checkpoint screening procedures, such as the PIL, develop sound evaluation methods to assist it in determining whether proposed procedures would achieve their intended result, such as enhancing the agency's ability to better detect prohibited items, and free up existing TSO resources. TSA conducted one evaluation on proposed X-ray screening procedures and one test on a proposed ETD procedure. Regarding the X-ray procedure change, TSA collected and analyzed the necessary data to determine whether the X-ray screening procedures would improve passenger throughput. However, in its evaluation of ETD devices, TSA was not able to provide documentation that explained the intended purpose of the proposed ETD procedure, the type of data TSA planned to collect, or how the data would be used. changes to standard operating procedures, as we recommended in April 2007. Without sound evaluation methods, TSA will be limited in its ability to determine whether proposed modifications to standard operating procedures--such as the PIL--will result in the intended risk reduction, for example, by enhancing the agency's ability to better detect IEDs and other high-risk items. TSA consulted both internal and external stakeholders during development of its decision to remove small knives from the PIL, but it did not adequately consult with several external aviation stakeholder groups. Some of these groups later raised strong objections after TSA publicly announced the change. GAO's Standards for Internal Control in the Federal Government states that an organization's management should ensure there are adequate means of communicating with, and obtaining information from, external stakeholders that may have a significant impact on the agency's operations and its achievement of organizational goals. These internal control standards further state that management is responsible for developing detailed policies, procedures, and practices to fit its agency's operations and to ensure that they are built into, and an integral part of, operations. Moreover, TSA's risk assessment and other planning documents leading up to its proposal to remove small knives from the PIL called for full coordination and collaboration with key external stakeholders who might have reservations about the change before moving forward with any revisions to the PIL. In coordinating with stakeholders, TSA primarily consulted with internal groups who, according to TSA, were generally supportive overall of the proposed revision. Specifically, TSA's efforts to coordinate with internal groups included the following: The TSA "Idea Factory": Provides for online comments from TSA personnel with "likes" and "dislikes" similar to those on Facebook. According to TSA, results received from April 2011 through December 2012 indicated that some TSA personnel, including screeners, thought that removing small knives would be a good idea and would improve their ability to screen for IEDs. TSA National Advisory Council: An internal employee advisory committee representing TSA employees at various levels, including management, supervisors, and TSOs. An ad hoc subcommittee of this council reviewed the PIL in July 2012 and recommended removing small knives. Administrator Pistole's informal discussions with TSOs: According to TSA, Administrator Pistole visited several airports, starting with a town hall meeting at Charlotte Douglas International Airport in December 2012, to gather input on the small knives proposal. TSA officials stated that, during these meetings, TSOs were supportive of the knives proposal and thought it would improve their ability to screen for explosive devices. Federal Air Marshal Service (FAMS): In February 2013, FAMS provided TSA management with comments that led to the small knives decision being more restrictive than TSA executives had originally considered. Specifically, the decision no longer allowed fixed or locking blades, or tactical or combat knives, regardless of length. FAMS officials stated they were generally opposed to allowing small knives on aircraft, but their concerns were mitigated by TSA management's revision of the proposal. TSA also reached out to some external stakeholder groups who, according to TSA, were also supportive of the decision to eliminate small knives, including the Airline Pilots Association, Families of September 11, and DHS's Homeland Security Advisory Council (HSAC). In addition, the TSA Administrator discussed possible changes to the Prohibited Items List in various appearances before Congress from 2010 to 2012 where he expressed the belief that screening personnel should concentrate on items that can cause catastrophic destruction of an aircraft. However, TSA did not discuss the proposal and solicit feedback from other relevant external stakeholders prior to its announcement. For example, TSA did not coordinate with or obtain input from the Aviation Security Advisory Committee (ASAC), which is its primary external advisory group for aviation security matters and whose membership includes various airline industry associations.stakeholders--from whom TSA did not adequately solicit feedback-- subsequently expressed strong opposition to the proposal, which contributed to TSA reversing its decision to implement the proposal. For example, TSA did not adequately consult with flight attendant groups during development of the small knives proposal, including the Association of Flight Attendants--an ASAC member--and the Coalition of Flight Attendant Unions. Specifically, in a November 30, 2012, phone call primarily regarding another matter, TSA informed the AFA president that it was also planning to modify the PIL to remove small knives. AFA officials disagreed with this decision. However, this conversation occurred after TSA had developed the proposal for the decision over the preceding months. Shortly after this meeting, the TSA Administrator approved the decision to remove small knives from the PIL, which was followed by the March 5, 2013, public announcement of the decision. In response to feedback received after its March 5, 2013, public announcement of the small knives decision, TSA conducted a classified briefing with the ASAC. TSA officials met with the ASAC on April 22, 2013, more than a month after TSA's March 5, 2013, public announcement of its proposed change and just prior to its planned implementation date of April 25, 2013, and briefed ASAC members on the announced change. Immediately following this meeting, and on the basis of input received by ASAC members and other stakeholders, the TSA Administrator announced a delay in implementation of the change to allow the agency additional time to more fully coordinate with various external stakeholders groups and incorporate additional input on the change. Following the ASAC briefing and announcement of the delay, TSA held similar briefings with other stakeholder groups including the Victims of Pan Am Flight 103 and the National Air Disaster Alliance/Foundation. On June 5, 2013, the TSA Administrator announced that on the basis of extensive engagement with the ASAC and other stakeholder groups, including law enforcement officials and passenger advocates, TSA would continue to enforce the current PIL and not go forward with the decision to remove small knives from the list. As described earlier, TSA management officials stated that they do not have a formal policy or a specific process for evaluating PIL modifications; this also means that they have no specific requirements for coordinating with stakeholders during development of potential revisions to the PIL. TSA officials stated that if some of the steps for stakeholder coordination defined in other TSA processes for emergency amendments and security directives had been in place for PIL changes--such as obtaining key stakeholder input when developing a security policy change--they may have helped to ensure better stakeholder coordination during consideration of the knives change. For example, TSA officials stated that, in hindsight, meeting with the ASAC and having more in- depth discussions with flight attendants during internal deliberations over modifying the PIL would have improved their efforts to fully coordinate and ensure they appropriately obtained and considered all key stakeholder perspectives. TSA officials also stated that they would have benefited from broader engagement earlier in the process with external groups, such as the ASAC and flight attendants. In the case of the small knives decision, the officials added that this broader and more timely engagement could have provided additional insight into the breadth and depth of potential concerns associated with removing certain items from the PIL. Clear processes outlining the appropriate types of stakeholders to consult--including when in the process stakeholders should be consulted--could help ensure that TSA's process for determining PIL changes is effective and efficient. For example, having clearly defined processes for stakeholder coordination could ensure that TSA fully obtains and considers stakeholder views--consistent with internal control standards and TSA's planning documents--that could help mitigate potential inefficiencies resulting from reversing policy decisions. Going forward, a formal process to ensure the solicitation of input from relevant external stakeholders on proposed changes to the PIL, including when in the PIL modification process TSA officials are to coordinate with such stakeholders, would help provide reasonable assurance that TSA has a more complete understanding of stakeholder perspectives earlier in the decision-making process. This could help avoid rescission of those changes after investing resources in training TSOs and informing the general public of the change, as was the case with the proposed change to remove small knives from the PIL. According to TSA personnel from the Office of Training Workforce and Engagement (OTWE), TSA evaluates on a case-by-case basis what training tools it will use to ensure TSOs are adequately trained to implement a change to the PIL. However, TSA typically provides TSOs with one or more of the following methods to prepare and train them to implement a PIL change: Online training--This type of training is web-based and may be completed by the TSOs either individually or as a group. This training may include test questions to assess the TSOs' mastery of the material. Instructor-led classroom training--Training personnel conduct formal classroom training with multiple TSOs. Informational briefings, bulletins, and memos--These include oral briefings by TSA trainers or supervisors in addition to notifications TSA headquarters sends to field personnel. These methods may be used to notify the field personnel of standard operating procedure changes or other matters. Trainers conduct briefings at the beginning of a TSO shift or may do so at another designated time, such as following a formal training session. The notifications sent by TSA headquarters may include "read and sign" memos, in the case of standard operating procedure changes, or may be presented online for other important matters. TSA training personnel stated that they maintain a flexible approach by using different methods to prepare TSOs to implement PIL changes since the changes have differed in their complexity, and therefore some PIL changes require less training and preparation than others. TSA training personnel stated they work closely with the Office of Security Operations (OSO) to determine the proper approach to prepare TSOs to implement each change. As an example of how the training approach can vary based on the nature of the PIL change, the TSA training officials cited the 2005 change to prohibit all lighters from sterile areas or aircraft as one that required less TSO preparation, in terms of training, compared with the 2013 proposal to remove small knives. This was because the small knives proposal encompassed more variables with regard to which knives could be allowed (e.g., length of knife, type of knife, etc.) and therefore required more evaluation and judgment on the part of the TSOs to implement and operationalize the change correctly. By contrast, for the lighters change, TSOs simply had to know they would not allow any lighters past the checkpoint. In developing training for the rollout of the small knives decision, TSA required all TSOs to complete web-based training, individually or as a TSA's web-based training group, covering the specifics of the change.was followed by a "training brief" that a TSA trainer would provide either (1) immediately following a web-based training group session or (2) as part of a "shift brief" at the beginning of TSOs' work period (after completion of the web-based session) in order to allow TSOs to ask questions and gain clarity on the specifics of the PIL change. TSA required TSOs to complete all training within a 20-day window prior to the planned implementation of the approved knives proposal. TSA's web-based training sessions on the knives decision included images that provided examples of knives and sporting equipment that would not be allowed under the new guidelines. As shown in figure 2, these examples included illustrations of knives that would not be allowed into secure areas or on board aircraft because of their size (length greater than 2.36 inches, width greater than 0.5 inch) and design features (e.g., locking blades, hand-molded grip, etc.) of knives that should be prevented from being carried into sterile areas and on board aircraft. In addition, the training included X-ray images to train TSOs on what an allowed and a disallowed knife would look like on the screen. TSA's web-based training also covered the new procedures associated with knives that TSOs were to follow at the checkpoint, such as requiring travelers to remove any knives they may be carrying from their carry-on baggage or their person so that these items may be screened separately. Last, the web training tested TSOs in their knowledge of the new guidelines for the upcoming PIL change. Similar to the web-based training, TSA's training brief included example images of allowed/disallowed knives and sporting equipment. The training brief also included coverage of the revised standard operating procedures associated with this PIL change. Proposals to add or remove items from TSA's PIL can have critical impacts, not just for the security of millions of air travelers each year, but on the efficiency and effectiveness of passenger screening at airport security checkpoints and perceptions of risk by external stakeholders. Making determinations about potential PIL changes can take time and extensive consideration on the part of TSA as the agency balances its aviation security goals with efficient passenger throughput. While we commend TSA's efforts to consider the risk posed by each item on the PIL, and potential screening efficiencies that may be created by allowing small knives and other items to be carried onto aircraft, conducting the analyses to demonstrate the potential efficiencies and to show that such efficiencies would offset the added risk presented by allowing small knives to be carried on board aircraft would help ensure that critical changes to the PIL will have the intended impact on both security and efficiency. These types of analyses would be consistent with the previous recommendation we made that TSA should strengthen its evaluation of proposed modifications to checkpoint screening procedures. Further, TSA stated in its risk assessment and other planning documents that it would be critical to involve stakeholders in its deliberations regarding the change to the PIL. However, by not taking the necessary steps to sufficiently consult with relevant external stakeholders who may be directly affected by the proposal to allow small knives onto aircraft, TSA ultimately reversed its decision to implement the small knives change to the PIL after having already publicly announced its decision and invested resources in training and implementation. Developing a formal process for stakeholder coordination when making changes to the PIL would help to ensure that TSA's decisions to change the PIL are fully informed by stakeholder perspectives, and help to ensure the efficient use of agency resources when revising and implementing PIL policies. To help ensure its proposed PIL modifications fully account for the views of key external stakeholders in the aviation industry, we recommend that the Transportation Security Administration's Administrator establish a formal process to ensure the solicitation of input from relevant external stakeholders on proposed changes to the PIL, including when in the PIL modification process TSA officials are to coordinate with such stakeholders, before deciding to make a PIL change. We provided a draft of this report to DHS for comment. DHS provided written comments, which are summarized below and reproduced in full in appendix I. TSA concurred with our recommendation and described actions planned to address it. In addition, DHS provided written technical comments, which we incorporated into the report as appropriate. In concurring with our recommendation, DHS agreed with the need for a formal process to ensure the solicitation of input from relevant external stakeholders on proposed changes to the PIL. DHS stated that TSA's senior leadership team works year-round to build and maintain strategic partnerships with various stakeholders to develop policy, share best practices, and participate in setting industry security standards, among other things, and that a formal process for making changes to the PIL will build upon these activities to ensure relevant stakeholders are offered the opportunity to engage with TSA and inform its decisions. DHS stated that a formal process should also make stakeholder engagement more disciplined and concise and result in decisions that are viable and acceptable. TSA has identified the Office of Security Policy and Industry Engagement and the Office of Security Operations as the appropriate offices to create such a process and plans for them to work closely with the Office of Intelligence and Analysis, the Office of the Chief Risk Officer, and the Office of Chief Counsel. TSA plans to create such a formal process by November 30, 2015. This process, when fully implemented, should address the intent of our recommendation. As agreed with your offices, unless you publicly announce the contents of this report earlier, we plan no further distribution until 30 days from the report date. At that time, we will send copies to the appropriate committees and the Secretary of Homeland Security. In addition, the report will be available at no charge on the GAO website at http://www.gao.gov. If you or your staff have any questions about this report, please contact me at (202) 512-7141 or groverj@gao.gov. Contact points for our Office of Congressional Relations and Public Affairs may be found on the last page of this report. Key contributors to this report are listed in appendix III. In addition to the contact named above, Chris Ferencik (Assistant Director), Dan Rodriguez (Analyst-in-Charge), Mike Harmond, Brendan Kretzschmar, Thomas Lombardi, Stanley Kostyla, Susan Hsu, Kathryn Godfrey, Linda Miller, and Eric Hauswirth made key contributions to this report.

Summary:
As part of its responsibilities for securing civil aviation, TSA ensures that all passengers and their accessible property are screened and prohibits individuals from carrying onto aircraft items that it determines to be a threat.TSA maintains a public list of such items, known as the Prohibited Items List, and updates it as necessary. In March 2013, TSA announced it would modify the PIL to allow small knives and certain sporting equipment onto aircraft, stating the change would result in more efficient security screening. However, several aviation industry groups opposed the decision, leading TSA to reverse its decision to implement the change. GAO was asked to review TSA's procedures for modifying the PIL. This report examines, among other issues, (1) on what basis TSA modifies the PIL and the extent to which TSA assessed risk when considering recent modifications to the PIL, and (2) the extent to which TSA involved stakeholders when considering these modifications. GAO reviewed TSA's standard operating procedures, risk assessment, documentation of its decisions and stakeholder outreach, and interviewed TSA officials at six airports. This is a public version of a report with Sensitive Security Information that GAO issued in December 2014. Information TSA deemed sensitive has been redacted. Transportation Security Administration (TSA) officials stated that TSA considers four factors when determining whether to make modifications to the Prohibited Items List (PIL), but the agency did not fully assess risk when considering its recent proposed PIL modifications, as GAO has previously recommended. TSA generally considers the following four factors when determining whether to modify the PIL: (1) the security risks posed by each carry-on item, (2) opportunities to improve screening operations and passenger experience, (3) harmonization with international security standards and practices, and (4) stakeholder perspectives. While TSA considered these four factors when making its March 5, 2013, decision to allow small knives and certain sporting equipment on aircraft, TSA officials also reasoned that the proposed change could help screening personnel focus less on lower-threat items, such as small knives, and more on higher-threat items, such as explosives, thereby potentially increasing security for passengers. However, TSA did not conduct sufficient analysis to show that the increased risk of allowing small knives on aircraft--as determined in its risk assessment--would be offset by a resulting reduction in risk from improved screening for explosives. GAO has previously recommended that TSA strengthen its evaluation methods for operationally testing proposed modifications to checkpoint screening procedures, including changes to the PIL. However, TSA has not consistently implemented this recommendation. Conducting additional risk analysis would have allowed TSA to actually measure whether airport screeners would be better able to identify explosives if they no longer had to screen for small knives. GAO continues to believe that TSA should develop and apply sound evaluation methods when considering modifications to the PIL, as GAO recommended in April 2007. TSA did not effectively solicit feedback on its 2013 PIL decision from relevant external stakeholders, some of whom subsequently expressed strong opposition to the decision to remove small knives from the PIL. For example, prior to announcing its decision, TSA did not coordinate with or obtain input from the Aviation Security Advisory Committee, which is TSA's primary external advisory group for aviation security matters and whose membership includes various airline industry associations. Some relevant stakeholders, such as flight attendant groups--from whom TSA did not adequately solicit feedback--subsequently expressed strong opposition to the proposal, which contributed to TSA reversing its decision to implement the change after having already trained screening personnel for its implementation. Having a defined process and associated procedures in place to communicate with relevant stakeholders earlier in the decision-making process could allow TSA to ensure appropriate consideration of their perspectives in the decision-making process. Use of a defined process and associated procedures could also allow TSA to better avoid rescission of any future changes after investing resources in training screening personnel and informing the general public of the change--as happened in the case of TSA's 2013 PIL decision. GAO recommends that TSA establish a formal process for soliciting input from relevant external stakeholders on proposed modifications to the PIL before making changes to it. DHS agreed with the recommendation.