Airport Passenger Screening: Preliminary Observations on Progress Made and Challenges Remaining
Published: 2003-09-24T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Passenger screening is critical to the security of our nation's aviation system, particularly in the aftermath of the September 11, 2001, terrorist attacks. The Transportation Security Administration (TSA) is tasked with securing all modes of transportation, including the screening of airline passengers. TSA has met numerous requirements in this regard, such as deploying more than 50,000 federal screeners at over 440 commercial airports nationwide. To determine whether TSA's passenger screening program is achieving its intended results, GAO is conducting an ongoing evaluation of TSA's efforts to (1) ensure that passenger screeners are effectively trained and supervised, (2) measure screener performance in detecting threat objects, and (3) implement and evaluate the contract screening pilot program.
section_title: What GAO Found
paragraphs: The Transportation Security Administration (TSA) was tasked with the tremendous challenge of building a large federal agency responsible for securing all modes of transportation, while simultaneously meeting ambitious deadlines to enhance the security of the nation's aviation system. Although TSA has made significant progress related to its passenger screening program, challenges remain. TSA recognized that ongoing training of screeners on a frequent basis, and effective supervisory training, is critical to maintaining and enhancing skills. However, TSA has not fully developed or deployed recurrent or supervisory training programs. Although TSA has not yet deployed these programs, it has taken steps in establishing recurrent and supervisory training, including developing six recurrent training modules that will soon be deployed to all airports, as well as working with the U.S. Department of Agriculture (USDA) Graduate School to tailor its off-the-shelf supervisory course to the specific training needs of TSA's screening supervisors. TSA currently collects little information regarding screener performance in detecting threat objects. The primary source of information collected on screener's ability to detect threat objects is covert testing conducted by TSA's Office of Internal Affairs and Program Review. However, TSA does not consider the results of these tests as a measure of screener performance, but rather a "snapshot" of a screener's ability to detect threat objects at a particular point in time. Additionally, TSA does not currently use the Threat Image Projection system, which places images of threat objects on x-ray screens during actual operations and records whether screeners identify the threat. However, TSA plans to fully activate the Threat Image Projection system with significantly more threat images than previously used, as well as implement an annual screener certification program in October 2003. TSA also recently completed a screener performance improvement study and is taking steps to address the deficiencies identified during the study. As required by the Aviation and Transportation Security Act, TSA implemented a pilot program using contract screeners in lieu of federal screeners at 5 commercial airports. However, TSA has not yet determined how to evaluate and measure the performance of the pilot program airports, or prepare for airports potentially applying to opt-out of using federal screeners, as allowed by the act, beginning in November 2004. Although TSA has not begun evaluating the performance of the pilot program airports, it plans to award a contract by October 1, 2003, to compare the performance of pilot screeners with federal screeners and determine the reasons for any differences. Numerous airport operators have contacted TSA to express an interest in obtaining more information to assist in their decision regarding opting-out of using federal screeners.

section_title: Letter
paragraphs: Passenger screening is a critical component to the security of our nation’s aviation system. Passenger screeners use metal detectors, X-ray machines,  explosive trace detection machines, and physical searches to examine  passengers and their baggage to identify threat objects. On November 19, 2001, prompted by the terrorist attacks of September 11, 2001, the  President signed the Aviation and Transportation Security Act (ATSA),  with a primary goal of strengthening the security of the nation’s aviation  system. ATSA created the Transportation Security Administration (TSA)  and mandated specific improvements to aviation security, including the federalization of passenger screening at over 440 commercial airports in  the United States by November 19, 2002.
TSA was tasked with the tremendous challenge of building a large federal  agency responsible for securing all modes of transportation, while  simultaneously meeting ambitious deadlines to federalize aviation security as mandated by ATSA. TSA has met numerous requirements related to its  passenger screening program, including deploying more than 50,000  federal screeners at over 440 commercial airports nationwide, developing and implementing a basic screener training program, and establishing a  pilot program at 5 airports where screening of passengers and property  would be conducted by private screening companies and overseen by TSA.
To determine whether TSA’s passenger screening program is achieving its  intended results, the Subcommittee on Aviation, House Committee on  Transportation and Infrastructure, requested that we review various  aspects of the program. Specifically, the Subcommittee asked that we  evaluate TSA’s efforts to (1) ensure that passenger screeners are  effectively trained and supervised, (2) measure screener performance in  detecting threat objects, (3) implement and evaluate the contract  screening pilot program, and (4) address airport-specific staffing needs,  while reducing the screener workforce. On September 5, 2003, we briefed  the Subcommittee staff on our preliminary observations of TSA’s  passenger screening program based on our work to date.
This report summarizes and updates the information presented at that  briefing. Because our work is still on going, the observations discussed in  this report are preliminary.
In conducting our work, we obtained and reviewed TSA documentation  related to screener training, testing and supervision; the contract  screening pilot program; screener staffing levels; and airport security  concerns. We also interviewed relevant officials at TSA headquarters and  field offices, airports, and several aviation associations. A more detailed  description of our scope and methodology is contained later in this report.
subsections: section_title: Background
paragraphs: ATSA created TSA as an agency within the Department of Transportation  (DOT) to ensure security for all modes of transportation, to include  aviation. ATSA set forth specific enhancements to aviation security for  TSA to implement and established deadlines for completing many of them.  These enhancements included federalizing passenger screeners at more  than 440 commercial airports by November 19, 2002; screening checked  baggage for explosives by December 31, 2002; enhancing screener training  standards; and establishing and managing a 2-year pilot program at five  airports—one in each airport category—where screening of passengers  and property would be conducted by a private screening company and  overseen by TSA. Additionally, ATSA included a provision that allows  airport operators to apply to opt-out of using federal screeners in favor of  private screeners beginning November 19, 2004.
Prior to the passage of ATSA, air carriers were responsible for screening  passengers and most used private security firms to perform this function.  Longstanding concerns existed regarding screener performance in  detecting threat objects. Inadequate training and poor supervision, along  with rapid turnover and inadequate attention to human factors, were  historically identified as key contributors to poor screener performance.As early as 1987, we reported that too little attention had been paid to  (1) individual aptitudes for effectively performing screening duties; (2) the  sufficiency of screener training and screeners’ ability to comprehend  training; and (3) the monotony of the job and distractions that reduced  screeners’ vigilance. Additional studies have shown that effective training  can lead to more effective performance and lower turnover rates for  passenger screeners.
Concerns have long existed over screeners’ inability to detect threat  objects during covert tests at passenger screening checkpoints. In 1978,  screeners failed to detect 13 percent of the potentially dangerous objects  FAA agents carried through checkpoints during tests—a level that was  considered “significant and alarming.” In 1987, screeners did not detect  20 percent of the objects during the same types of tests. In addition, we  reported that FAA tests conducted between 1991 and 1999 showed that  screeners’ ability to detect objects was not improving, and in some cases  was worsening. In tests conducted in the late 1990s, as the testing objects  became more realistic and more closely approximated how a terrorist  might attempt to penetrate a checkpoint, screeners’ ability to detect  dangerous objects declined even further.
section_title: Scope and Methodology
paragraphs: Our preliminary observations are based on our review of TSA  documentation related to screener training, testing, and supervision; the  contract screening pilot program; screener staffing levels; and airport  security concerns. We interviewed TSA headquarters’ officials in  Arlington, Virginia; and interviewed FSDs, their staffs, and screeners at  12 commercial airports throughout the nation; 10 airport operators;  officials at 5 air carriers; and officials from 4 aviation associations—  American Association of Airport Executives (AAAE), Airports Council  International (ACI), Air Transport Association, and Regional Airline  Association. We also reviewed our prior reports that addressed issues  related to the performance of airport passenger screeners. We conducted  our work from May through September 2003 in accordance with generally  accepted government auditing standards. Because our review is still  ongoing, the results presented in this report are preliminary.
To complete our work, we will continue to collect and review TSA  documentation related to each of our four objectives, including obtaining  and analyzing the results of TSA’s operational tests. We will also  administer a survey to all 158 FSDs to obtain their perspectives on general  and airport specific information related to each of our four objectives.  Additionally, we will visit at least 8 additional airports to conduct  interviews with FSDs, their staffs, members of the screener workforce,  and airport operators. We will also interview representatives of all 5 pilot  program airports, as well as airport operators at all category X airports, to  obtain information on their coordination with TSA and their plans, if any,  to apply to opt-out of the federal screening program beginning November  19, 2004. Finally, we will continue to meet with TSA headquarters officials  to obtain current information related to the issues addressed in this report.  We anticipate issuing a final report in April 2004.
section_title: Recurrent and Supervisory Training Programs Not Fully Developed
paragraphs: TSA developed basic and remedial screener training programs, but has not  fully developed or deployed a recurrent or supervisory training program to  ensure that screeners are effectively trained and supervised.  Comprehensive and frequent training is key to passenger screeners’ ability  to detect threat objects. Studies have shown that on-going training can  lead to more effective performance and lower turnover rates for passenger  screeners. According to TSA, there are three key elements of passenger  screener training: (1) basic training, (2) remedial training, and  (3) recurrent training. As required by ATSA, TSA established a basic  screener-training program comprised of 40 hours of classroom instruction  and 60 hours of on-the-job training (OJT). TSA reported that all of its  screeners who work independently have completed basic screener  training and that those who failed an operational test received required  remedial training.
subsections: section_title: Basic Training
paragraphs: TSA requires screeners to complete a minimum of 40 hours of classroom  instruction and 60 hours of OJT prior to making independent screening  decisions. This requirement is an increase over FAA’s basic training  requirements when it oversaw passenger screening, which called for  12 hours of classroom instruction and 40 hours of OJT. According to TSA  officials, all screeners who work independently have met the basic  screener training requirements. TSA contractors are responsible for  delivering and tracking basic screener classroom training, while OJT is  tracked locally at each airport. TSA encourages, but does not require,  screening managers, who are responsible for overseeing screening  functions to participate in classroom training, even if they do not have  prior screening experience. Nevertheless, 2 of the 12 FSDs we interviewed  said that they require their screening managers to observe basic screener  training.
section_title: Remedial Training
paragraphs: Consistent with ATSA, TSA requires remedial training for any screener  who fails an operational test and prohibits screeners from performing the  screening function related to the test they failed until they successfully  complete the training. FSDs must certify that screeners identified as  requiring remedial training complete the training before they can perform  the screening function identified as a performance weakness. TSA’s  Aviation Operations Division is responsible for tracking the completion of  remedial training following the failure of covert tests. The tracking of  remedial training initiated for reasons other than failing a covert test is the  responsibility of the FSDs or their designees. TSA reported that all  screeners requiring remedial training have received the training.
section_title: Recurrent Training
paragraphs: TSA has not fully developed or deployed a recurrent training program, but  has recognized that ongoing training of screeners on a frequent basis is  critical to maintaining and enhancing screener skills. According to agency  officials, TSA established a training task force comprised of airport  Training Coordinators, screeners, and headquarters officials to conduct an  assessment of training needs. As a result of the task force’s suggestions,  TSA is developing six recurrent training modules—the first of which TSA  plans to deploy to all airports beginning in October 2003. TSA plans to  release each of the remaining five modules as they are finalized, which  they anticipate will occur throughout 2004. TSA officials also said that  they designed and are currently pilot testing an On-Line Learning  Management System (LMS) comprised of 366 various training courses,  which they expect to field in October 2003. Officials said that they were  not further along in implementing their recurrent training modules or LMS  due to budget considerations.
Fourteen of the 22 passenger screeners and supervisors we interviewed  expressed the need for recurrent training. They were particularly  interested in receiving additional training related to recognizing x-ray  images of threat objects. In addition, 10 of the 12 FSDs we interviewed  reported implementing their own locally developed recurrent training  courses rather than waiting for the training modules to be deployed by  headquarters. TSA’s OIAPR found that screeners at airports that  conducted frequent, on-going training performed better during covert  tests—TSA’s form of operational testing—than screeners who did not  receive recurrent training.
section_title: Supervisory Training
paragraphs: TSA describes its screening supervisors as the key to a strong defense in  detecting threat objects. In September 2001, we reported on the results of  our survey of aviation stakeholders and aviation and terrorism experts  concerning options for conducting screening. The respondents identified  better supervision as one of the factors necessary for improving screener  performance. Additionally, DOT’s Office Inspector General (OIG)  recently reported that screener supervisors are the key to effective  screening, and TSA’s OIAPR identified a lack of supervisory training as a  cause for screener testing failures. FSDs and TSA headquarters officials  recognize the need to enhance the skills of screening supervisors through  supervisory training.TSA is currently working with USDA to tailor its off- the-shelf supervisory course to the specific needs of TSA’s screening  supervisors. TSA recently reported that it is sending supervisors to the  basic USDA supervisor’s course until the customized course is fielded,  which it expects to occur in April 2004. To supplement the classroom  training, TSA also plans to establish a supervisory training module for  recurrent training. We plan to review TSA’s training initiatives further  during the remainder of our evaluation.
section_title: Little Information Exists to Measure Screeners’ Performance in Detecting Threat Objects
paragraphs: Currently, the results of TSA’s OIAPR’s operational, or covert, testing is  the only indication of screener performance in detecting threat objects.  However, TSA does not view the results of OIAPR’s covert testing as a  measure of screener performance, but rather as a “snapshot” of a  screener’s ability to detect threat objects at a particular point in time.  Although OAIPR conducts fewer covert tests of passenger screeners than  previously conducted by the FAA, TSA considers its tests more rigorous  than FAA’s tests because they more closely approximate techniques  terrorists might use. In addition to conducting operational testing, TSA  plans to fully activate the Threat Image Projection system and implement a  screener certification program in October 2003 to collect additional  information on screener performance. TSA also developed a Performance  Management Information System to collect and maintain information on  the performance of its passenger and baggage screening operations.  However, PMIS contains little data on screener performance in detecting  threat objects. TSA officials said that they plan to expand PMIS to collect  some performance information, but did not identify a timeframe for when  the data will be collected.
subsections: section_title: Operational Testing
paragraphs: TSA defines an operational screening test as any covert test of a screener,  conducted by TSA, on any screener function to assess the screener’s threat  item detection ability and/or adherence to TSA-approved procedures.  When a screener fails a test, he or she is required to receive immediate  remedial training, and is prohibited from performing the function related  to the failed test until he or she satisfactory completes the training.  Currently, OIAPR’s covert testing is the only source of operational testing  conducted of passenger screeners. These tests are designed to identify  systematic problems affecting the performance of screeners in the areas of  training, policy, and equipment. TSA does not view the results of OIAPR’s  covert testing as a measure of screener performance, but rather a  “snapshot” of a screener’s ability to detect threat objects at a particular  point in time and as an indicator of systemwide screener performance.  OIAPR testing to date has shown weaknesses in screeners’ ability to detect  threat objects. Testing conducted by the DOT’s OIG, the Department of  Homeland Security’s OIG, and GAO have also identified screener  performance weaknesses.
Prior to the creation of TSA, FAA conducted thousands of covert tests  annually of passenger screeners. Most of these tests were compliance tests  in which FAA agents attempted to get nine test objects, such as guns and  grenades, past screeners conducting x-ray, metal detector, and physical  searches at airport checkpoints. The DOT OIG described these tests as  unlike the techniques that terrorists would employ. In 1997, FAA  incorporated simulated improvised explosive devices into its compliance  testing and performed, on average, more than 2,000 of these test each year.  In addition to compliance tests, FAA’s special headquarters based testing  unit, often called the Red Team, conducted more realistic tests using  harder to detect threat objects by agents not known to screeners.
TSA’s OIAPR has conducted fewer covert tests than conducted by FAA,  but considers its testing methods more rigorous than either of FAA’s  compliance or Red Team tests because they more closely approximate  techniques terrorists might use. OIAPR officials further said that their tests  are intentionally designed to have a high probability of failure in an effort  to identify vulnerabilities and areas needing improvement. Additionally,  unlike testing conducted under FAA, OIAPR staff that perform the tests  reported that they provide immediate feedback to screeners, their  managers, and the FSDs to explain how they beat the system and provide  instant remedial training. We plan to review OIAPR’s operational testing in  more detail during the remainder of our evaluation.
Based on an anticipated increase in staff from about 100 in fiscal year 2003  to 200 in fiscal year 2004, OIAPR plans to conduct twice as many covert  tests next year. In addition, TSA recently established 5 mission support  centers located throughout the country, which according to TSA, will be  staffed with OIAPR personnel available to conduct additional covert  tests. These centers will also be staffed with mobile testing teams that  will work with FSDs in their region to conduct screener training using  some of the test objects OIAPR uses in its covert tests.
section_title: Threat Image Projection (TIP) System
paragraphs: In late 1999, to help screeners remain alert, train them to become more  adept at detecting harder to spot threat objects, and continuously measure  screener performance, FAA began deploying TIP. TIP places images of  threat objects on x-ray screens during actual operations and records  whether screeners identify the threat object. By frequently exposing  screeners to a variety of images of dangerous objects on the x-ray screens,  the system provides continuous OJT and allows for immediate supervisory  feedback, on-the-spot training, and remedial training.
According to TSA officials, TIP was shut down immediately following the  September 11th terrorist attacks due to concerns that it would result in  screening delays and panic, as screeners might think that they were  actually viewing a threat object. TSA officials recognize that TIP is a key  tool in maintaining and enhancing screener performance, and said that  they had begun reactivating TIP with significantly more images than FAA  had in place. TSA officials said that TIP had not been reactivated sooner  due to a lack of automated data collection via cellular modems; competing  priorities; a lack of training; and a lack of resources needed to deploy TIP  activation teams.
section_title: Annual Screener Certification
paragraphs: ATSA requires that each passenger screener receive an annual proficiency  review to ensure he or she continues to meet all qualifications and  standards required to perform the screening function. Although TSA has  not yet implemented this requirement, it plans to develop an annual  screener certification program comprised of three components, including  (1) image recognition test; (2) knowledge of standard operating  procedures (SOPs); and (3) practical demonstration of skills, to be  administered by a contractor. TSA has not yet determined the level of  performance that screeners must achieve to be certified, but officials said  that they plan to require performance at a high, but reasonable level.  Officials also said that they plan to remediate and retest screeners who fail  any portion of the test, but have not yet determined the number of times a  screener may retake the test before termination. Certification is scheduled  to begin in October 2003 and to be completed at all 442 airports by January  2004, in the order in which the airports began federal screening  operations. TSA officials recently reported that they awarded a contract to  conduct the practical demonstration component of the test; however, TSA  has not developed a schedule for when the program will be fielded to the  airports. We plan to review TSA’s annual screener certification program  during the remainder of our evaluation.
section_title: Performance Management Information System
paragraphs: TSA’s Performance Management Information System—PMIS—for  passenger and baggage screening operations contains little data on  screener performance in detecting threat objects. PMIS collects  information on workload, staffing, and equipment and is used to identify  some performance and policy issues, such as the level of absenteeism,  average time for equipment repairs, and status of TSA’s efforts to meets  goals for 100 percent baggage screening. (See app. I for examples of  information collected and contained in PMIS.) Additionally, TSA uses  PMIS data to identify needed changes to SOPs. Officials further reported  that PMIS has the ability to generate reports that enable TSA to track its  progress toward meeting its performance goals as well as to generate  reports by region, FSD, airport, and/or individual screening checkpoint.  PMIS has been deployed to all airports with federal screeners. FSDs are  responsible for designating a staff person to enter performance data into  PMIS on a daily basis.
TSA officials reported that they are planning to integrate performance  information from various systems into PMIS to assist the agency in making  strategic decisions. TSA also recently reported that it is developing a  screener performance index, which is supposed to include information  such as the results of TIP tests, training tests, and certification tests. We  plan to review these plans in more detail during the remainder of our  evaluation.
section_title: Screener Performance Improvement Study
paragraphs: TSA is taking steps to improve screener performance. In July 2003, TSA  completed a Screener Performance Improvement Study, which was  designed to identify root causes for gaps between current screener  performance and TSA’s desired performance—defined as 100 percent  interception of prohibited items coming through the passenger screening  checkpoints. As part of its study, TSA identified four significant screener  performance deficiencies. TSA concluded that four key factors  contributed to the identified deficiencies: (1) lack of skills, knowledge, or  information; (2) low motivation; (3) ineffective work environment; and  (4) incorrect or missing incentives. To address the screener performance  deficiencies identified in the study, TSA developed several key solutions,  including the need to establish adequate training facilities at airports; staff  airports adequately to allow time for training; reconfigure checkpoints to  eliminate distractions; implement TIP at all airports; and enhance  supervisory skills. According to TSA officials, the appropriate TSA  components are currently developing action plans for each of the  deficiencies identified in the Performance Improvement Study. The plans  are to include action steps, timelines, required resources, and anticipated  outcomes. We plan to review these plans during the remainder of our  evaluation.
section_title: An Assessment of the Contract Screening Pilot Program Has Not Yet Begun
paragraphs: TSA has implemented a pilot program using contract screeners at  5 airports, but has not determined how to evaluate and measure the  performance of the pilot program airports. The purpose of the 2-year pilot  program is to determine the feasibility of using private screening  companies rather than federal screeners. Initially, TSA required private  screening companies to adhere to all of the procedures and protocols used  for federal screeners. However, TSA recently provided the pilot  contractors with some flexibility, such as allowing them to determine and  maintain their own staffing levels and make independent hiring decisions.  While TSA has not yet determined how to evaluate and measure the  performance of the pilot program airports, it plans to award a contract by  October 1, 2003, to compare the performance of pilot screeners with  federal screeners and determine the reasons for any differences. TSA  officials said that the Office of Management and Budget requested that  they include in their evaluation ways to allow more innovation by contract  screening companies.
Although ATSA allows airports to apply to opt-out of using federal  screeners beginning in November 2004, TSA has not begun to plan for the  possible transition of airports from a federal system to a private screening  company. Airports Council International officials said that numerous  airports have contacted them expressing an interest in obtaining more  information to assist in their decision regarding opting-out. Six of the 10  airport operators we interviewed said that they had not made any  decisions regarding opting-out, and all 10 said they had not received any  information from TSA regarding the option. However, the airport  operators said that they would like information to assist them in deciding  whether to opt-out, such as determining who bears responsibility for  funding the screening contract; airport liability in the event of an incident  linked to a screener failure; how well the current pilot program airports  are performing; performance standards to which contract screeners will  be held; and TSA’s role in overseeing contracted screening.
section_title: TSA Continuing to Work to Identify Appropriate Staffing Levels at the Nation’s Airports
paragraphs: Initially, TSA headquarters determined screener-staffing levels for all  airports without actively seeking input from FSDs. Eight of the 12 FSDs  we interviewed said that they had limited authority to respond to airport  specific staffing needs, such as reacting to fluctuations in daily and/or  seasonal passenger flow. However, TSA headquarters officials said that  during the second stage of their workforce reduction process, they  solicited input from FSDs, airport officials, and air carriers. TSA  headquarters officials acknowledged that their initial staffing efforts  created imbalances in the screener workforce and have taken steps to  correct identified imbalances, such as such as authorizing the hiring of  part-time screeners at over 200 airports—the first of which began working  on September 15, 2003.
TSA determined the current screener staffing levels using a computer- based modeling process that took into account the number of screening  checkpoints and lanes at an airport; originating passengers; the number of  airport workers requiring screening; projected air carrier service increases  and decreases during calendar year 2003; and hours needed to  accommodate screener training, leave, and breaks. TSA recently hired an  outside consultant to conduct a study of screener staffing levels at various  airports. TSA officials stated that they will continue to review the staffing  allocation provided through the modeling efforts to assess air carrier and  airport growth patterns, and adjustments will be made as appropriate. We  plan to review TSA’s efforts to determine appropriate staffing levels for  passenger screeners during the remainder of our evaluation.
As agreed with your office, unless you publicly announce its contents  earlier, we plan no further distribution of this report until 5 days after its  issue date. At that time, we will send copies of this report to the Secretary  of the Department of Homeland Security and interested congressional  committees. We will also make copies available to others upon request. In addition, the report will be available at no charge on GAO’s Web site at  http://www.gao.gov.
If you have any questions about this report, or wish to discuss it further,  please contact me at (202) 512-8777 or Jack Schulze, Assistant Director, at  (202) 512-4390. Key contributors to this report are listed in appendix II.
section_title: Appendix I: Examples of Information Maintained in TSA’s Performance Management Information System
paragraphs: Number of weapons surrendered at sweep screening  Number of cleared Explosive Trace Detection (ETD) alarms  Lost, stolen, or damaged items  Number of Screeners on light duty  Number of screeners trained on baggage only/passenger only/cross- trained  Percent of airports using the CAPPS II system  Average wait time at passenger screening checkpoints for federalized  airports  Number of gates in use  Number of ETS, x-ray machines, explosive detection systems (EDS)  machines  Number of enplanements  Number of screeners on duty  Individual airport measures to achieve change in threat level by date and  time  TSA officials described sweep screening as a method of screening in which screeners randomly stop  passengers in the airport concourse for additional screening.
section_title: Appendix II: GAO Contacts and Staff Acknowledgments
subsections: section_title: GAO Contacts
section_title: Staff Acknowledgments
paragraphs: In addition to those named above, David Alexander, Lisa Brown,  Christopher Jones, Stuart Kaufmann, Thomas Lombardi, Jan Montgomery,  Edward Stephenson, Maria Strudwick, and Susan Zimmerman were key  contributors to this report.