Passenger screening is a process by which personnel authorized by TSA inspect individuals and property to deter and prevent the carriage of any unauthorized explosive, incendiary, weapon, or other dangerous item onboard an aircraft or into a sterile area. Passenger screening personnel must inspect individuals for prohibited items at designated screening locations. As shown in figure 1, the four passenger screening functions are X-ray screening of property, walk-through metal detector screening of individuals, hand-wand or pat-down screening of individuals, and physical search of property and trace detection for explosives. Typically, passengers are only subjected to X-ray screening of their carry- on items and screening by the walk-through metal detector. Passengers whose carry-on baggage alarms the X-ray machine, who alarm the walk- through metal detector, or who are designated as selectees—that is, passengers selected by the Computer-Assisted Passenger Prescreening System (CAPPS) or other TSA-approved processes to receive additional screening—are screened by hand-wand or pat-down and have their carry- on items screened for explosives traces or physically searched. The passenger checkpoint screening system is composed of three elements: the people responsible for conducting the screening of airline passengers and their carry-on items—TSOs, the technology used during the screening process, and the procedures TSOs are to follow to conduct screening. Collectively, these elements help to determine the effectiveness and efficiency of passenger checkpoint screening. TSOs screen all passengers and their carry-on baggage prior to allowing passengers access to their departure gates. There are several positions within TSA that perform and directly supervise passenger screening functions. Figure 2 provides a description of these positions. In May 2005, we reported on TSA’s efforts to train TSOs and to measure and enhance TSO performance. We found that TSA had initiated a number of actions designed to enhance passenger TSO, checked baggage TSO, and supervisory TSO training. However, at some airports TSOs encountered difficulty accessing and completing recurrent (refresher) training because of technological and staffing constraints. We also found that TSA lacked adequate internal controls to provide reasonable assurance that TSOs were receiving legislatively mandated basic and remedial training, and to monitor the status of its recurrent training program. Further, we reported that TSA had implemented and strengthened efforts to collect TSO performance data as part of its overall effort to enhance TSO performance. We recommended that TSA develop a plan for completing the deployment of high-speed Internet/intranet connectivity to all TSA airport training facilities, and establish appropriate responsibilities and other internal controls for monitoring and documenting TSO compliance with training requirements. DHS generally concurred with our recommendations and stated that TSA has taken steps to implement them. There are typically four types of technology used to screen airline passengers and their carry-on baggage at the checkpoint: walk-through metal detectors, X-ray machines, hand-held metal detectors, and explosive trace detection (ETD) equipment. The President’s fiscal year 2007 budget request noted that emerging checkpoint technology will enhance the detection of prohibited items, especially firearms and explosives, on passengers. As of December 2006, TSA plans to conduct operational tests of three types of passenger screening technologies within the next year. TSA has conducted other tests in the past; for example, during fiscal year 2005, TSA operationally tested document scanners, which use explosive trace detection technology to detect explosives residue on passengers’ boarding passes or identification cards. TSA decided not to expand the use of the document scanner, in part because of the extent to which explosives traces had to be sampled manually. TSA also plans to begin operational tests of technology that would screen bottles for liquid explosives. We are currently evaluating the Department of Homeland Security’s and TSA’s progress in planning for, managing, and deploying research and development programs in support of airport checkpoint screening operations. We expect to report our results in August 2007. TSA has developed checkpoint screening standard operating procedures, which are the focus of this report, that establish the process and standards by which TSOs are to screen passengers and their carry-on items at screening checkpoints. Between April 2005 and December 2005, based on available documentation, TSA deliberated 189 proposed changes to passenger checkpoint screening SOPs, 92 of which were intended to modify the way in which passengers and their carry-on items are screened. TSA issued six versions of the passenger checkpoint screening SOPs during this period. TSA modified passenger checkpoint screening SOPs to enhance the traveling public’s perception of the screening process, improve the efficiency of the screening process, and enhance the detection of prohibited items and suspicious persons. As shown in table 1, 48 of the 92 proposed modifications to passenger checkpoint screening SOPs were implemented, and the types of modifications made or proposed generally fell into one of three categories—customer satisfaction, screening efficiency, and security. TSA used various processes between April 2005 and December 2005 to modify passenger checkpoint screening SOPs, and a variety of factors guided TSA’s decisions to modify SOPs. TSA’s processes for modifying SOPs generally involved TSA staff recommending proposed modifications, reviewing and commenting on proposed modifications, and TSA senior leadership making final decisions as to whether proposed modifications should be implemented. During our 9-month review period, TSA officials considered 92 proposed modifications to the way in which passengers and their carry-on items were screened, and 48 were implemented. TSA officials proposed SOP modifications based on risk factors (threat and vulnerability information), day-to-day experiences of airport staff, and concerns and complaints raised by passengers. TSA then made efforts to balance security, efficiency, and customer service when deciding which proposed SOP modifications to implement. Consistent with our prior work that has shown the importance of data collection and analyses to support agency decision making, TSA conducted data collection and analysis for certain proposed SOP modifications that were tested before they were implemented at all airports. Nevertheless, we found that TSA could improve its data collection and analysis to assist the agency in determining whether the proposed procedures would enhance detection or free up TSO resources, when intended. In addition, TSA did not maintain complete documentation of proposed SOP modifications; therefore, we could not fully assess the basis for proposed SOP modifications or the reasons why certain proposed modifications were not implemented. TSA officials acknowledged that it is beneficial to maintain documentation on the reasoning behind decisions to implement or reject SOP modifications deemed significant. Proposed SOP modifications were submitted and reviewed under two processes during our 9-month review period, and for each process, TSA senior leadership made the final decision as to whether the proposed modifications would be implemented. One of the processes TSA used to modify passenger checkpoint screening SOPs involved TSA field staff or headquarters officials, and, to a lesser extent, TSA senior leadership, suggesting ways in which passenger checkpoint screening SOPs could be modified. These suggestions were submitted through various mechanisms, including electronic mail and an SOP panel review conducted by TSA airport personnel. (These methods are described in more detail in app. II.) Eighty-two of the 92 proposed modifications were considered under this process. If TSA officials determined, based on their professional judgment, that the recommended SOP modifications—whether from headquarters or the field—merited further consideration, or if a specific modification was proposed by TSA senior leadership, the following chain of events occurred: First, the procedures branch of the Office of Security Operations drafted SOP language for each of the proposed modifications. Second, the draft language for each proposed modification was disseminated to representatives of various TSA divisions for review, and the language was revised as needed. Third, TSA officials tested proposed modifications in the airport operating environment if they found it necessary to: assess the security impact of the proposed modification, evaluate the impact of the modification on the amount of time taken for passengers to clear the checkpoint, measure the impact of the proposed modification on passengers and industry partners, or determine training needs created by the proposed modification. Fourth, the revised SOP language for proposed modifications was sent to the heads of several TSA divisions for comment. Fifth, considering the comments of the TSA division heads, the head of the Office of Security Operations or other TSA senior leadership made the final decision as to whether proposed modifications would be implemented. Another process for modifying passenger checkpoint screening SOPs during our 9-month review period was carried out by TSA’s Explosives Detection Improvement Task Force. The task force was established in October 2005 by the TSA Assistant Secretary to respond to the threat of improvised explosive devices (IED) being carried through the checkpoint. The goal of the task force was to apply a risk-based approach to screening passengers and their baggage in order to enhance TSA’s ability to detect IEDs. The task force developed 13 of the 92 proposed SOP modifications that were considered by TSA between April 2005 and December 2005. The task force solicited and incorporated feedback from representatives of various TSA divisions on these proposed modifications and presented them to TSA senior leadership for review and approval. TSA senior leadership decided that 8 of the 13 proposed modifications should be operationally tested—that is, temporarily implemented in the airport environment for the purposes of data collection and evaluation—to better inform decisions regarding whether the proposed modifications should be implemented. Following the testing of these proposed modifications in the airport environment, TSA senior leadership decided to implement 7 of the 8 operationally tested changes. (The task force’s approach to testing these procedures is discussed in more detail below.) Following our 9-month period of review, the changes that TSA made to its passenger checkpoint screening SOPs in response to the alleged August 2006 liquid explosives terror plot were decided upon by DHS and TSA senior leadership, with some input from TSA field staff, aviation industry representatives, and officials from other federal agencies.