United States Government Accountability Office

GAO Report to the Ranking Democratic

Member, Committee on Transportation 

and Infrastructure, House of 

Representatives 

AVIATION SECURITY

TSA Oversight of 

Checked Baggage 

Screening Procedures 

Could Be 

Strengthened 

July 2006 

 

GAO-06-869 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

July 2006

AVIATION SECURITY

TSA Oversight of Checked Baggage 

Screening Procedures Could Be 

Strengthened 

Highlights of GAO-06-869, a report to the 

Ranking Democratic Member, Committee 

on Transportation and Infrastructure, 

House of Representatives

TSA has prioritized standard and alternative checked baggage screening 

procedures based on legislative requirements and TSA officials’ judgment of 

the procedures’ effectiveness. Use of various procedures to screen checked 

baggage has involved trade-offs in security effectiveness, which vary by the 

type of procedure used and the circumstances of its use. It is TSA’s policy to 

use standard procedures whenever possible because TSA officials 

determined that these procedures provide the most effective detection of 

explosives. TSA policy also allows the use of alternative screening 

procedures when volumes of baggage awaiting screening pose security

vulnerabilities or when TSA airport officials determine that there is a

security risk associated with large concentrations of passengers in an area 

waiting for their baggage to be screened. Regarding operational efficiencies, 

TSA has not fully determined the throughput and costs of the various 

alternative screening procedures in part because it does not count the 

number of bags screened using these procedures. TSA has conducted covert 

tests (undercover, unannounced) of standard procedures, but has not 

conducted this testing for alternative screening procedures. TSA cited 

logistical difficulties in conducting covert tests for alternative screening 

procedures. However, by not doing so, TSA is not collecting data that could 

provide useful information in determining the security effectiveness of the 

procedures in an operational setting and how to improve their effectiveness. 

TSA cannot identify the percentage of checked baggage screened using 

standard versus alternative screening procedures because TSA records 

standard procedures in terms of the number of bags screened in its 

management information system, but records alternative procedures in 

terms of the number of occasions and hours of use. However, TSA officials 

estimated that a low percentage of checked baggage is screened using 

alternative screening procedures. To assess the extent that standard 

screening procedures are used whenever possible, TSA has established 

internal controls to monitor the use of standard and alternative screening 

procedures; however, these controls were not always implemented to ensure

the gathering of complete and accurate information. This may limit TSA 

managers’ ability to assess the effect of using alternative screening 

procedures and determine what should be done to minimize the use of the 

procedures. TSA headquarters officials stated that they are working with 

TSA airport staff to correct such reporting problems. 

TSA has taken steps to reduce the need to use alternative screening 

procedures at airports, including anticipating factors that could increase 

passenger and baggage volume and acting to address these factors. 

However, TSA has not developed performance measures and targets to 

assess its progress in minimizing the need to use the procedures. By creating 

performance measures, TSA could gauge whether it is making progress 

toward minimizing the need to use alternative screening procedures at 

airports. Performance targets for the procedures would be an indicator of 

how much risk TSA is willing to accept in using the procedures. 

www.gao.gov/cgi-bin/getrpt?GAO-06-869.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Cathleen 

Berrick at (202) 512-3404 or

berrickc@gao.gov. 

The Transportation Security 

Administration (TSA) is 

responsible for screening all 

checked baggage in U.S. airports

for explosives and has deployed 

explosive detection systems and 

developed standard procedures for 

their use. TSA also allows 

alternative screening procedures to

be used for short-term, special 

circumstances. This report

addresses (1) how TSA prioritized 

the use of checked baggage 

screening procedures and 

identified trade-offs in security

effectiveness and operational 

efficiencies; (2) how TSA reported 

use of the procedures and ensured 

that standard procedures are used

whenever possible; and (3) what 

steps TSA took to reduce airports’ 

need to use alternative screening 

procedures and to establish 

performance measures to monitor 

their use. To address these issues,

GAO interviewed TSA officials, 

reviewed information from TSA’s 

database on checked baggage 

screening operations; and 

conducted airport site visits.

What GAO Recommends

GAO is recommending that TSA 

use information on airport usage of

alternative screening procedures in

conducting covert testing;

strengthen TSA’s monitoring and 

tracking of the use of alternative 

screening procedures; and develop 

performance measures and targets 

for the use of alternative screening 

procedures. DHS reviewed a draft 

of this report and generally

concurred with GAO’s findings and 

recommendations.
Contents 

Letter 1

Results in Brief 5

Background 9

TSA Prioritized Screening Procedures Based on Legislative 

Requirements and Judgment of Effectiveness but Has Not 

Tested the Security Effectiveness of Alternative Screening 

Procedures in an Operational Environment 14 

The Full Extent of the Usage of Alternative Screening Procedures 

Is Not Known, and Internal Controls for Monitoring the Usage of 

Baggage Screening Procedures Could Be Improved 21 

TSA Has Taken Action to Reduce the Need to Use Alternative 

Screening Procedures, but Has Not Implemented Performance 

Measures or Targets 25 

Conclusions 31

Recommendations for Executive Action 33 

Agency Comments and Our Evaluation 34 

Appendix I Objectives, Scope, and Methodology 37 

Appendix II Comments from the Department of Homeland 

Security 40 

Appendix III GAO Contact and Staff Acknowledgments 43 

Related GAO Products 44 

Table 

Table 1: Bags per Hour Screened Using Standard Screening 

Procedures for Stand-alone and In-line EDS Machines and 

ETD Machines 16 

Page i GAO-06-869 Aviation Security
Figures 

Figure 1: EDS Machines In a Stand-alone Configuration Used by 

TSA to Screen Checked Baggage 11 

Figure 2: ETD Machine Used by TSA to Screen Checked Baggage 12 

Abbreviations 

ATSA Aviation and Transportation Security Act 

DHS Department of Homeland Security 

EDS Explosive Detection System 

ETD Explosive Trace Detection 

FAA Federal Aviation Administration 

FSD Federal Security Director 

GPRA Government Performance and Results Act 

OI Office of Inspections 

PMIS Performance Management Information System 

TSA Transportation Security Administration 

TSO Transportation Security Officer 

This is a work of the U.S. government and is not subject to copyright protection in the 

United States. It may be reproduced and distributed in its entirety without further 

permission from GAO. However, because this work may contain copyrighted images or 

other material, permission from the copyright holder may be necessary if you wish to 

reproduce this material separately. 

Page ii GAO-06-869 Aviation Security
United States Government Accountability Office

Washington, DC 20548 

July 28, 2006

The Honorable James L. Oberstar 

Ranking Democratic Member 

Committee on Transportation and Infrastructure 

House of Representatives 

Dear Mr. Oberstar: 

Commercial U.S. aircraft have long been a target for terrorist attacks 

through the use of explosives carried in checked baggage, as 

demonstrated by the 1988 bombing of a U.S. aircraft over Lockerbie, 

Scotland. After the terrorist attacks of September 11, 2001, which further 

highlighted the vulnerability of U.S. aircraft to acts of terrorism, Congress 

passed and the President signed into law the Aviation and Transportation 

Security Act (ATSA), mandating, among other things, that all checked

baggage at U.S. airports be screened using explosive detection systems by 

December 31, 2002.1

 In response to this mandate, the Transportation 

Security Administration (TSA) has deployed two types of systems and has 

established standard procedures for their use: (1) explosive detection 

systems (EDS) that use specialized X-rays to detect characteristics of 

explosives that may be contained in baggage as it moves along a conveyor 

belt and (2) explosive trace detection (ETD) systems, whereby an 

individual (i.e., a baggage screener) swabs a bag and then inserts the swab 

into the ETD machine, which, in turn, can detect chemical residues that 

may indicate the presence of explosives within a bag.2

 TSA also allows 

alternative screening procedures to be used when volumes of baggage 

awaiting screening pose security vulnerabilities or when TSA officials 

determine that there is a security risk associated with large concentrations 

of passengers in an area. These alternative screening procedures include 

the use of EDS and ETD machines in nonstandard ways,3

 and also include 

three procedures that do not use EDS or ETD—screening with explosives 

detection canines, physical bag searches, and matching baggage to 

 1

Congress subsequently extended this deadline by 1 year. 

2

TSA interpreted ATSA’s reference to “explosive detection systems” to allow for the 

deployment of EDS and ETD to satisfy the mandate. 

3

The nonstandard ways that the machines are used is sensitive security information. 

Page 1 GAO-06-869 Aviation Security
passenger manifests to confirm that the passenger and his or her baggage 

are on the same plane. It is TSA’s policy to use standard EDS and ETD 

screening procedures whenever possible and, when necessary, to use EDS 

or ETD-based alternative screening procedures before using non-EDS or 

ETD alternative screening procedures. TSA has also established operating

procedures for checked baggage screening that instruct Transportation 

Security Officers (TSO—formerly known as screeners) in how to use these 

standard and alternative screening procedures. 

In February 2004, we testified that TSA was unable to fully utilize 

explosive detection systems to satisfy the ATSA mandate to screen 

100 percent of checked baggage for explosives because of TSO shortages 

and problems with screening equipment, among other factors.4

 Further, in 

February 2005, we reported that TSA considers one baggage screening 

method—the use of EDS machines—to be the superior baggage screening 

procedure in terms of efficiency compared to ETD because EDS 

automatically detects explosives without direct human involvement and 

screens more bags for explosives per hour. We also reported that at most 

smaller airports, where EDS machines are not installed, TSA screens 

solely with ETD machines. Finally, we reported that while TSA had made 

progress in deploying EDS and ETD machines, it had not conducted a 

systematic, prospective analysis of the optimal deployment of these 

machines to achieve long-term savings and enhanced efficiencies and 

security. In February 2006, TSA issued a report to Congress detailing its 

strategic planning framework for its checked baggage screening program. 

According to TSA, the framework, which focuses on identifying optimal 

checked baggage screening solutions for airports, will be used to establish 

a comprehensive strategic plan for TSA’s checked baggage screening 

program. TSA expects to complete the strategic plan in early fall 2006. 

You asked that we continue to assess TSA’s progress in enhancing the 

effectiveness of checked baggage screening operations. In February 2006,

we issued a report that contained sensitive security information regarding

TSA’s use of standard and alternative checked baggage screening 

procedures, including the extent to which the procedures were used by 

TSA and the trade-offs in security effectiveness of using standard and 

alternative screening procedures to screen checked baggage for 

 4

GAO, Aviation Security: Challenges Exist in Stabilizing and Enhancing Passenger and

Baggage Screening Operations, GAO-04-440T (Washington, D.C.: Feb. 12, 2004). 

Page 2 GAO-06-869 Aviation Security
explosives.5

 We concurrently issued a classified correspondence on our 

analysis of the results of TSA’s checked baggage screening covert testing.

6

This report provides the results of our February 2006 report with sensitive 

security information removed. In this report, we address the following 

questions: (1) How did TSA prioritize the use of standard and alternative 

checked baggage screening procedures and what security effectiveness 

trade-offs and operational efficiencies has TSA identified in using these 

procedures to screen checked baggage for explosives? (2) To what extent 

has TSA used standard and alternative screening procedures to screen 

checked baggage for explosives and how does TSA ensure that standard 

screening procedures are used whenever possible? (3) What steps has TSA 

taken to reduce airports’ need to use alternative screening procedures and 

to establish performance measures and targets for the use of the 

procedures? 

To address how TSA prioritized the use of checked baggage screening 

procedures and identified trade-offs in security effectiveness and 

operational efficiencies of using standard and alternative screening 

procedures to screen checked baggage for explosives, we assessed TSA’s 

standard operating procedures, obtained and analyzed relevant legislation, 

and conducted a literature search to obtain information on screening 

procedures, technologies, and related aviation trends. We also reviewed 

studies conducted by TSA’s Transportation Security Laboratory regarding

checked baggage screening. We interviewed officials from various TSA 

offices as well as air carriers, explosive detection systems equipment 

manufacturers, and an airport industry association to obtain information 

regarding TSA’s checked baggage screening procedures and the relative

priority they were given. To determine the extent to which TSA used 

standard and alternative screening procedures to screen checked baggage

and how TSA ensured that standard screening procedures are used 

whenever possible, we reviewed TSA’s checked baggage standard 

operating procedures manual and its Performance Management 

Information System (PMIS) database, which contains information on 

checked baggage screening operations.7

 We compared TSA procedures for 

 5

GAO, Aviation Security: TSA Management of Checked Baggage Screening Procedures 

Could Be Improved, GAO-06-291SU (Washington, D.C.: Feb. 28, 2006). 

6

GAO, Analysis of TSA’s Covert Testing for Checked Baggage Screening, GAO-06-317C

(Washington, D.C.: Feb. 28, 2006). 

7

PMIS is a Web-based application used by TSA field staff to submit data to headquarters on 

operations and performance. 

Page 3 GAO-06-869 Aviation Security
use of standard and alternative screening procedures with the Comptroller 

General’s Standards for Internal Control in the Federal Government. We 

interviewed TSA officials to determine the reliability of the information 

contained in the PMIS database and reviewed selected database records. 

Although we determined that the database did not always contain accurate 

data on the duration of each occurrence of alternative baggage screening

procedures, we nonetheless considered the database to be sufficiently 

reliable for purposes of this report since the data identified overall trends

in the use of alternative screening procedures. To assess the steps TSA has 

taken to reduce airports’ need to use alternative screening procedures and 

the measures and targets TSA has set for alternative screening procedures,

we analyzed TSA directives regarding use of the procedures, PMIS data, 

standard operating procedures for checked baggage, and the inventory of 

explosive detection systems. When we found discrepancies in the 

inventory data of explosive detection systems, we worked with TSA to 

resolve the discrepancies. TSA also completed a reconciliation of the 

inventory database with data collected manually by TSA officials. We also

examined TSA’s checked baggage screening performance measures and 

targets as they relate to the Government Performance and Results Act of 

1993 (GPRA) requirements. We visited nine airports during this review to 

observe baggage screening operations. We chose these airports based on 

reporting in PMIS, selecting some airports that had used alternative 

screening procedures and some that had not used the procedures. We also

conducted structured interviews with TSA Federal Security Directors 

(FSD)8

 and their staffs who were responsible for the security of 

29 randomly selected airports. Because we selected a nonprobability 

sample of airports to visit, the information we obtained during these visits 

cannot be generalized to all airports nationwide.9

 Also, while the 

interviews we conducted with FSDs were random samples of airports, the 

samples were too small to generalize the interview results with a high 

degree of statistical confidence to all airports nationwide. 

 8

The Federal Security Director is the ranking TSA authority responsible for the leadership

and coordination of TSA security activities at the nation’s commercial airports. 

9

Nonprobability sampling is a method of sampling where observations are selected in a 

manner that is not completely random, usually using specific characteristics of the 

population as criteria. Results from nonprobability samples cannot be used to make

inferences about a population because in a nonprobability sample, some elements of the 

population being studied have no chance or an unknown chance of being selected as part

of the sample. 

Page 4 GAO-06-869 Aviation Security
We conducted our work from August 2004 through July 2006 in 

accordance with generally accepted government auditing standards. A 

more detailed discussion of our scope and methodology is contained in 

appendix I. 

TSA prioritized the use of standard and alternative checked baggage 

screening procedures based on legislative requirements and TSA officials’ 

judgment of the effectiveness of the procedures, and TSA’s use of these 

procedures has involved trade-offs in security effectiveness. It is TSA’s 

policy to use standard EDS and ETD screening procedures whenever 

possible because of legislative requirements to do so and because TSA has 

concluded that these procedures provide the most effective detection of

explosives at a checked baggage screening station. TSA considers 

screening with EDS to be superior to screening with ETD because EDS 

machines process more bags per hour and automatically detect explosives 

without direct human involvement. Given the high volumes of checked 

baggage processed at some airports and unforeseen events such as 

equipment failures and severe weather, TSA has determined that it will 

have to continue to at times use alternative screening procedures to 

screen checked baggage for explosives. TSA officials prioritized the use of

these procedures based on their professional judgment of the 

effectiveness of the procedures and the classified probabilities of 

detection of EDS and ETD machines obtained from the TSA 

Transportation Security Laboratory. Alternative screening procedures 

include physical bag searches; alternative hybrid procedures, which 

involve a combination of the standard checked baggage procedures for 

EDS and ETD;10 matching checked bags to passenger manifests to deter 

bombers who try to load a bag on a plane without boarding; explosive 

detection canines; and another screening method TSA has determined to 

be sensitive security information. With regard to operational efficiencies, 

TSA has not determined the throughput (number of checked bags 

screened per hour) and costs of the various alternative screening 

procedures in part because it does not count the number of bags screened 

using these procedures. While TSA has used alternative screening 

procedures for more than 3 years and expects to continue to use them, it 

has not tested the security effectiveness of these procedures in an 

Results in Brief 

 10Alternative hybrid procedures use a combination of EDS and ETD at a screening station 

that is usually configured only for EDS. At some screening stations, TSA has also allowed 

the use of a hybrid configuration as a standard screening procedure. 

Page 5 GAO-06-869 Aviation Security
operational environment. TSA has conducted national covert (undercover, 

unannounced) testing of standard screening procedures since September 

2002 to assess checked baggage screening technologies and procedures,

and TSO performance in detecting explosives in an operational 

environment. TSA has also authorized FSDs and their designates to 

conduct local covert testing on standard screening procedures at airports 

since March 2005 to determine if TSOs can detect simulated improvised 

explosive devices hidden in checked baggage. However, TSA has not 

conducted national or local covert testing specifically focused on 

alternative screening procedures. TSA officials stated that conducting 

national testing of alternative screening procedures would be challenging, 

particularly since testing is planned ahead of time and it is difficult to 

predict when an airport might use alternative screening procedures. While 

it may be logistically difficult to conduct national covert testing on 

alternative screening procedures, TSA data on which airports most 

frequently use the procedures and the reasons for the usage could provide

TSA with information to use in selecting airports for covert testing as part 

of the risk-based approach to covert testing that it is developing. TSA 

officials also cited challenges in conducting local covert testing of 

alternative screening procedures, including the difficulty in predicting the 

need to use the procedures and the lack of available federal staff to 

conduct the testing, particularly at smaller airports. Because FSDs and 

their staffs authorize and initiate the use of alternative screening 

procedures, they could schedule some of their ongoing local covert testing

for checked baggage screening to coincide with the use of these 

procedures. In not assessing the alternative screening procedures through 

covert testing, TSA is not collecting data that could help determine how 

effective the procedures are in an operational setting or how to improve 

the security effectiveness of the procedures. 

TSA reported using both standard and alternative screening procedures in 

PMIS but could not identify the percentage of all checked baggage

screened using EDS and ETD with standard or alternative screening 

procedures. TSA could not identify the percentage of usage of standard or 

alternative screening procedures because for standard screening 

procedures, PMIS contains data on the number of bags screened; whereas 

for alternative screening procedures, it contains data on the number of 

occasions and hours of use. However, TSA officials estimated that a high

percentage of checked baggage is screened using EDS and ETD machines 

Page 6 GAO-06-869 Aviation Security
with standard screening procedures11 and a low percentage is screened 

using alternative screening procedures.12 TSA also established internal 

controls to monitor and track the use of standard and alternative 

screening procedures, including requiring FSDs to report the use of 

alternative screening procedures into PMIS and to call headquarters for 

permission to use the alternative screening procedures for more than 

2 hours. According to the Comptroller General’s Standards for Internal 

Control, all transactions and other significant events need to be 

completely and accurately documented. However, we identified several 

areas where TSA’s information on its use of standard and alternative 

screening procedures was not complete or accurate for the period covered

by our review. First, TSA’s method for estimating the number of bags 

screened with ETD using standard screening procedures led to inaccurate

counts of baggage screened. Improved counting of bags would provide 

TSA management with better information to use in making decisions 

related to its baggage screening operations including where to deploy 

screening equipment. Second, FSDs and their staffs did not always 

accurately report the occurrences when a particular alternative baggage 

screening procedure was used, impeding TSA’s ability to reliably 

determine how often and for how long the alternative screening 

procedures were used. Third, FSDs and their staffs did not always report 

the use of alternative screening procedures as required. Inaccurate and

incomplete reporting on how often alternative screening procedures are 

used or for how long, combined with not tracking the number of bags 

screened using the procedures, may limit TSA managers’ ability to assess 

the effect of using alternative screening procedures on aviation security 

and to determine the types of actions that should be taken at airports to 

help minimize the use of these procedures. TSA officials stated they are 

working with FSDs to correct these reporting problems and have issued 

guidance clarifying requirements for reporting alternative screening 

procedures. 

 11TSA does not require airports to report information on the number of bags screened using

alternative screening procedures. To derive its estimate of use of alternative screening 

procedures across the system, TSA used alternative screening procedures baggage counts

only from those airports that voluntarily reported the information in order to calculate the 

average number of bags screened per hour. TSA then used this calculation of the average

bags per hour and the total number of screening hours using the procedures to make this

estimate. Because TSA did not have baggage counts for all of the occurrences of alternative

screening procedures, this estimate may be inaccurate. 

12TSA determined that the estimated use of alternative screening procedures is sensitive 

security information. 

Page 7 GAO-06-869 Aviation Security
TSA has taken steps to reduce airports’ need to use alternative screening 

procedures, but has not established performance measures or targets 

regarding the use of these procedures. According to our review of PMIS 

data, the use of alternative screening procedures between October 2004 

and September 2005—measured in terms of the total hours of use reported 

by FSDs—initially increased and then declined.

13 TSA attributed the 

reported overall decline in the use of alternative screening procedures to a 

number of factors, including better coordination with groups such as tour 

operators; deploying “optimization teams” to airports that were frequently 

using alternative screening procedures to determine why the procedures 

were being used so often and to suggest remedies; and deploying 

additional EDS machines.14 As we reported in March 2005, additional EDS 

systems integrated into the airport baggage handling system (“in-line” EDS 

systems) could reduce by 78 percent the number of baggage TSOs and 

supervisors needed to screen checked baggage at airports with the 

systems.15 TSA’s February 2006 checked baggage screening planning 

framework includes a prioritization of which additional airports should 

receive new funding for in-line systems and a description of how standalone EDS machines from those airports should be redistributed to other 

airports. After in-line EDS systems are installed and any staffing 

reductions are achieved, redistributing the screening positions to other 

airports with staffing shortages could also reduce the need to use 

alternative screening procedures at these airports. While TSA data indicate 

that the use of alternative screening procedures is declining, the strategic 

planning framework states that at some airports alternative screening 

procedures will increasingly be used because of rising passenger traffic. 

TSA has projected that the number of originating domestic and 

international passengers will rise by about 127 million passengers over 

current levels by 2010, which could increase airports’ need to rely on 

alternative screening procedures in the future in the absence of additional

or more efficient EDS machines. Furthermore, while TSA has taken steps 

to reduce the need to use alternative screening procedures at airports, it 

 13The specific details on the number of hours alternative screening procedures were used

are sensitive security information. 

14At 46 airports, a combined total of 154 EDS machines were added; at 22 airports, a

combined total of 62 EDS machines were removed; and 47 airports maintained the same 

number of EDS machines. One airport with two EDS machines in inventory in 2005 was not 

on the 2004 or 2002 inventory lists. 

15GAO, Aviation Security: Systematic Planning Needed to Optimize the Deployment of 

Checked Baggage Screening Systems, GAO-05-365 (Washington, D.C.: Mar.15, 2005). 

Page 8 GAO-06-869 Aviation Security
has not created performance measures or targets regarding its progress in 

minimizing the need to use alternative screening procedures at airports. 

By creating performance measures for the use of alternative screening 

procedures and corresponding targets, TSA could gauge whether it is 

making progress in working to minimize the need to use alternative 

screening procedures at airports and to consider the necessity to take 

further steps to minimize the need for their use. 

To help strengthen TSA’s management of checked baggage screening 

operations, including screening with alternative screening procedures, we 

are recommending that the Secretary of the Department of Homeland 

Security (DHS) direct the Assistant Secretary, TSA, to use PMIS data on 

the use of alternative screening procedures at airports to help determine 

which airports to conduct national covert testing at and when to conduct

such testing, to conduct local covert testing of alternative screening 

procedures, to strengthen its monitoring and tracking of the use of 

alternative screening procedures, and to develop performance measures 

and performance targets for the use of alternative screening procedures. 

We provided a draft copy of this report to DHS for review. DHS, in its 

written comments, generally concurred with our findings and 

recommendations and stated that the recommendations and findings will 

help strengthen TSA’s management of checked baggage screening 

operations. The full text of DHS’s comments is included in appendix II. 

ATSA mandated that the screening of all checked baggage at commercial 

airports be done using explosive detection systems by December 31, 2002.

To satisfy this mandate, TSA deployed two types of screening equipment 

to all airports in the United States where screening is required: 

(1) explosive detection systems, which use computer-aided tomography16

X-rays adapted from the medical field to automatically recognize the 

characteristic signatures of threat explosives, and (2) explosives trace 

detection systems, which use chemical analysis to detect traces of 

Background 

Standard Procedures for 

Using EDS and ETD 

 16Computer-aided tomography is a method of producing a three-dimensional image of the 

internal structures of a solid object by the observation and recording of the differences in

the effects on the passage of waves of energy impinging on those structures. 

Page 9 GAO-06-869 Aviation Security
explosive materials’ vapors and residues. As we reported in February 2004, 

largely because of shortages of equipment and insufficient time to modify 

airports to accommodate EDS machines, TSA was unable, at certain 

airports, to meet this deadline. Recognizing the obstacles encountered by 

TSA, the Homeland Security Act of 2002, in effect, subsequently extended

the deadline for screening all checked baggage for explosives until 

December 31, 2003, for airports at which TSA was unable to meet the 

earlier deadline established by ATSA. We also reported that TSA fell short 

of fully satisfying the extended 2003 mandate and continued to face 

challenges in screening checked baggage because of (1) an insufficient 

number of TSOs to operate the EDS and ETD machines, TSO absenteeism, 

and a lack of TSO training in how to operate the machines and (2) a lack

of EDS and ETD equipment and inoperable equipment.17

By taking the equivalent of hundreds of X-ray pictures of a bag from 

different angles, the EDS machine examines the objects inside of the 

baggage to identify the characteristic signatures of threat explosives such 

as density and atomic number. TSA has certified, acquired, and deployed

EDS machines manufactured by three companies. EDS machines can be

installed in airports either in stand-alone mode (not integrated with 

baggage handling systems) or in-line (integrated with baggage handling 

systems). TSA has developed standard procedures for using EDS. Figure 1

shows EDS machines in use at an airport. 

 17GAO-04-440T. 

Page 10 GAO-06-869 Aviation Security
Figure 1: EDS Machines In a Stand-alone Configuration Used by TSA to Screen

Checked Baggage

Source: GAO.

At airports that do not have EDS machines and at airports where certain

screening stations do not have EDS—for example at curbside check-in 

stations—TSA uses ETD machines to conduct primary screening. ETD 

machines are also used for secondary screening, which resolves alarms 

from EDS machines that indicate the possible presence of explosives 

inside a bag. TSA has certified, acquired, and deployed ETD machines 

from three manufacturers. Figure 2 shows an ETD machine in use at an 

airport. 

Page 11 GAO-06-869 Aviation Security
Figure 2: ETD Machine Used by TSA to Screen Checked Baggage

Source: GAO.

At some screening stations, TSA has also allowed primary screening with

both EDS and ETD machines simultaneously. In this hybrid configuration, 

the EDS machine is used to maximum capacity before the ETD machines 

are used. Additionally, when the EDS machine alarms, the ETD machines 

are also used for secondary screening. 

Alternative Screening 

Procedures 

TSA also uses alternative screening procedures to screen checked baggage

for explosives under certain short-term special circumstances, when the 

standard procedures using EDS and ETD are not used. Two of these 

procedures involve the use of EDS and ETD. The first of these is an 

alternative hybrid procedure that is used at a screening station configured

only for EDS primary screening. Under this procedure, the EDS is to be 

used to capacity and the remainder of the bags are screened with ETD. 

Page 12 GAO-06-869 Aviation Security
The specifics of the second procedure that involves the use of EDS and 

ETD are sensitive security information.18 If one of these EDS- or ETDbased alternative screening procedure is not available, TSA will resort to 

one of the procedures that does not use EDS or ETD—canine screening;

physical inspections of baggage; and positive passenger bag match, which 

requires that passengers be on the same aircraft as their checked 

baggage.19

FSDs and their designates not lower than the Assistant FSD for Screening 

may authorize the use of alternative screening procedures under two 

circumstances: (1) when the FSD or his or her designate determines that 

there is a security threat created by large concentrations of passengers 

waiting to have their baggage screened or (2) volumes of baggage awaiting 

screening in a confined baggage screening area pose an explosive or other

security vulnerability. These circumstances may arise for reasons such as 

high passenger volumes, screening machine breakdowns, or unusual 

weather events such as hurricanes. After alternative screening procedures 

have been used, TSA requires that information on each occurrence be

recorded by FSD staff into the PMIS database, including circumstances 

leading to the use of the procedure, type of procedure used, and duration.

This information on the use of alternative screening procedures from PMIS 

is to be included in daily briefing reports for TSA senior management. 

 18 TSA also moved additional ETD machines to screening stations to allow for ETD 

screening. Prior to March 2005, TSA had categorized this procedure, “additional ETDs,” as

an alternative screening procedure. Beginning in March 2005, TSA began to categorize this

procedure as a standard screening procedure. We did not include this procedure in our

analysis of PMIS data on alternative screening procedures. 

19ATSA, as codified at 49 U.S.C. §44901(d)-(e), authorizes TSA to screen checked baggage 

using canine screening, physical inspection, or a bag match program if explosive detection 

equipment is unavailable. 

Page 13 GAO-06-869 Aviation Security
TSA prioritized standard and alternative checked baggage screening 

procedures based on legislative requirements and TSA officials’ judgment

of the security effectiveness of the procedures. TSA’s use of these various

procedures has involved trade-offs in security effectiveness. TSA officials 

determined that in general, standard screening procedures are more 

effective than alternative screening procedures. TSA has estimated that in

terms of efficiency, EDS processes more bags per hour than ETD. With 

regard to operational efficiencies, TSA has not determined the throughput 

and costs of the various alternative screening procedures, in part because

it does not count the number of bags screened using the procedures. 

Additionally, while TSA has assessed the security effectiveness of 

screening with standard procedures in an operational environment 

through covert testing, it has not conducted similar testing of alternative 

screening procedures. 

TSA is required by legislation to screen all checked baggage using 

explosive detection systems, and TSA officials concluded that standard 

screening procedures that use EDS or ETD provided the most effective 

detection of explosives at a baggage screening station and that alternative 

screening procedures should be used only for short-term, special 

circumstances. These circumstances include times when security targets 

are created by large volumes of passengers awaiting baggage screening or 

when security vulnerabilities are created by volumes of bags awaiting 

screening. According to TSA, a group of officials from its Chief 

Technologist, Chief Counsel, Aviation Operations, and Operations Policy 

offices met to prioritize the use of standard and alternative screening 

procedures. TSA officials stated that this group did not use formal criteria 

to prioritize the procedures but instead prioritized them based on their 

professional judgment of the effectiveness of the procedures, including the 

classified probabilities of detection of EDS and ETD machines obtained 

from the Transportation Security Laboratory. This prioritization was 

subsequently included in TSA’s standard operating procedures for 

checked baggage screening. TSA has determined that details on the 

prioritization of alternative screening procedures constitute sensitive 

security information. 

TSA Prioritized 

Screening Procedures 

Based on Legislative 

Requirements and 

Judgment of 

Effectiveness but Has 

Not Tested the 

Security Effectiveness 

of Alternative 

Screening Procedures 

in an Operational 

Environment 

TSA Prioritized Standard 

and Alternative Screening 

Procedures Based on 

Legislative Requirements 

and TSA Officials’ 

Judgment of Security 

Effectiveness 

Page 14 GAO-06-869 Aviation Security
TSA has estimated that, in terms of efficiency, EDS processes more bags 

per hour than ETD—EDS ranges from a minimum of 80 bags per hour for 

one model of a stand-alone machine up to 500 bags per hour for an in-line 

system, compared to 36 bags per hour by the operator of an ETD 

machine.20 Whenever EDS machines have been installed at a screening 

station, TSA requires airports to use them as the primary method to screen 

checked baggage. At some screening stations, TSA has also allowed the 

use of a hybrid configuration as a standard screening procedure that 

involves colocated EDS and ETD machines for primary screening, with the 

EDS machine used to maximum capacity before the ETD machines are 

used. When the EDS machine alarms, the ETD machines are also used for 

secondary screening. Table 1 shows the bags per hour screened by EDS 

and ETD machines. 

Standard Baggage 

Screening Procedures Vary 

in Operational Efficiency 

 20TSA officials stated that two TSOs can use an ETD machine at the same time, raising the 

baggage screened throughput to 72 bags per hour 

Page 15 GAO-06-869 Aviation Security
Table 1: Bags per Hour Screened Using Standard Screening Procedures for 

Stand-alone and In-line EDS Machines and ETD Machines 

Type of equipment Maximum bags per hour

EDS machines Stand-alone In-line

CTX 2500—stand-alone only 120 NAa

CTX 5500 180 250

CTX 9000—in-line only NA 500

L3 6000 140 500

CT-80—stand-alone only 80 NA

ETD machines—stand-alone only 36 MA

Source: TSA. 

a

NA: Not applicable. 

At 312 mostly smaller airports and at some airport screening stations such 

as curbside check-in stations, TSA has installed ETD instead of EDS for 

primary screening because of the configuration of screening stations, the 

costs associated with procuring EDS, and the low passenger volume at 

smaller airports. In our March 2005 report, we recommended that TSA 

assess the feasibility, expected benefits, and cost to replace ETD machines 

with stand-alone EDS machines for the primary screening of checked

baggage at those airports where in-line EDS systems would not be either 

economically justified or justified for other reasons. 21 DHS stated that TSA

was conducting an analysis of the airports that rely heavily on ETD 

machines as the primary checked baggage screening technology in order 

to identify airports that would benefit from replacing ETD machines with 

stand-alone EDS equipment.22 In February 2006, in response to GAO’s 

recommendation and a legislative requirement to submit a schedule for 

expediting the installation and use of in-line systems and replacement of 

ETD equipment with EDS machines, 23 TSA provided its strategic planning 

framework for its checked baggage screening program to Congress. This 

framework introduces a strategy intended to increase efficiency through 

 21GAO-05-365. 

22The stand-alone EDS equipment TSA is considering for these airports includes surplus

machines no longer needed once airports installed in-line EDS machines and a newly 

certified EDS machine appropriate for baggage screening operations that require a lower 

throughput (bags screened per hour). 

23Intelligence Reform and Terrorism Prevention Act of 2004, Pub. L. No. 108-458, § 4019, 

118 Stat. 3638, 3721-22. 

Page 16 GAO-06-869 Aviation Security
deploying EDS to as many airports as practicable, lower life-cycle costs for 

the program, minimize impacts to TSA and airport/airline operations, and 

provide a flexible security infrastructure for accommodating growing 

airline traffic and potential new threats.24 The framework is an initial step 

in addressing the following areas: 

• optimized checked baggage screening solutions—finding the ideal mix of 

higher-performance and lower-cost alternative screening solutions for the 

250 airports with the highest checked baggage volumes and 

• funding prioritization schedule by airport—identifying the top 25 airports

that should first receive federal funding for projects related to the 

installation of explosive detection systems based on quantitative modeling 

of security, economic, and other factors. 

TSA’s strategic plan for the checked baggage screening program, which 

TSA expects to complete by early fall 2006, is to include funding and costsharing strategies for the installation of in-line baggage screening systems. 

TSA has determined that the use of alternative screening procedures at 

airports has created trade-offs in security effectiveness, but it has not 

determined the operational efficiencies of these procedures in terms of 

throughput and costs.25 TSA based its prioritization of the alternative 

screening procedures on its judgment of the procedures’ security 

effectiveness and classified probabilities of detection of EDS and ETD 

machines obtained from the TSA Transportation Security Laboratory. TSA 

has not determined the operational efficiencies of the various alternative

screening procedures in terms of throughput and costs in part because it

does not count the number of bags screened using the procedures. If the 

higher-prioritized alternative screening procedure is not available at a 

screening station, the FSD may authorize a lower-prioritized procedure.26

Use of Alternative Baggage 

Screening Procedures 

Involves Trade-offs in 

Security Effectiveness, 

while Trade-offs in 

Operational Efficiencies 

Have Not Been 

Determined 

 24TSA has determined that the details of its analysis of the optimal checked baggage 

screening solutions are sensitive security information. 

25The specifics of the trade-offs in security effectiveness have been determined to be

sensitive security information.

26One alternative screening procedure that involves the use of EDS and ETD is not 

discussed in this report because TSA designated the procedure as sensitive security 

information. 

Page 17 GAO-06-869 Aviation Security
Under the positive passenger bag match alternative screening procedure, 

TSA coordinates with airlines to ensure that passengers are on the same 

aircraft as their checked baggage. If a passenger checks a bag but does not

board the airplane, the bag is removed before departure. This procedure 

was first implemented based on the premise that a terrorist would seek to 

place a bomb on an airplane without sacrificing his or her life by boarding 

the airplane. In light of the suicide terrorist attacks of September 11, this

premise is now considered flawed. An airline trade association and airline 

officials representing two airlines we interviewed also stated that the 

procedure creates operational inefficiencies for airlines. According to 

these officials, the process of matching bags with passengers can delay 

flights because the flight cannot take off until all baggage is matched to an 

on-board passenger. These officials also stated that implementing the 

procedure increases the workload of airline personnel, who are 

responsible for conducting the procedures at the direction of TSA. 

TSA also uses canine units as an alternative screening procedure. These 

units are composed of trained explosives detection canines and handlers. 

In terms of efficiency, TSA officials reported that it can be difficult to 

mobilize canine units in sufficient time to screen checked baggage when 

alternative screening procedures are needed, especially since the need to 

use the procedures can arise without warning. Officials also reported that 

screening checked baggage using canines requires enough open floor 

space to lay out the baggage as well as a sufficient number of personnel to 

move the bags into position for canine screening.

The physical inspection alternative screening procedure requires human 

intervention to detect explosives, weapons, and improvised explosive 

devices and their components, and does not involve use of EDS or ETD 

machines. While TSOs are trained to detect improvised explosive devices 

and their components and to detect signs of tampering, the success of the 

TSOs in finding these items depends on their skill in detecting such items 

through manual searches and their adherence to TSA’s standard operating

procedures for checked baggage regarding physical inspection. Since 

human TSOs are involved, the efficiency of physical inspection in terms of 

baggage throughput rate can vary depending on the contents of the bag 

and how quickly the TSO conducts the search. 

Alternative hybrid procedures involve using a combination of EDS and 

ETD at a screening station normally configured only for EDS. The 

efficiency of alternative hybrid procedures can vary because each use of 

the procedure can involve a different proportion of EDS and ETD 

Positive Passenger Bag Match 

Canine Screening 

Physical Inspection 

Alternative Hybrid Procedures 

Page 18 GAO-06-869 Aviation Security
screening, with greater use of EDS leading to more efficient screening in 

terms of number of bags screened per hour. 

While TSA has reported using alternative screening procedures for more 

than 3 years, it has not tested the security effectiveness of the procedures 

in detecting explosives in an operational environment. TSA has conducted 

national covert testing of standard screening procedures since September 

2002, and local covert testing of standard screening procedures since 

March 2005. However, it has not specifically focused national or local 

covert testing on alternative screening procedures to determine the 

security effectiveness of the procedures. TSA’s Office of Inspections (OI— 

formerly the Office of Internal Affairs and Program Review) conducts 

national covert tests at airports to assess the security effectiveness of 

checked baggage screening technology, procedures, and TSO performance 

in detecting explosives in an operational environment. These tests, in 

which undercover inspectors attempt to pass threat objects through 

passenger screening checkpoints and in checked baggage, are designed to 

identify vulnerabilities in passenger and checked baggage screening 

systems and to identify systematic problems affecting screening in the 

areas of training, procedures, and technology.27 The schedule for this 

testing called for inspectors to test all category X airports once a year, 

category I and II airports once every 2 years, and category III and IV 

airports at least once every 3 years.28 In August, 2005, TSA suspended this 

cycle of testing. In April 2006, TSA officials stated that OI was moving to a 

testing schedule to include observations of screening stations and 

concentrated testing for improvised explosive devices at the screening 

checkpoint. The schedule is based on risk-based factors such as current 

intelligence information, high-vulnerability airports, procedural changes, 

training initiatives, and introduction of new technologies. According to 

Office of Inspections officials, during the 3-year testing cycle, inspectors 

tested the procedures being used by TSOs at the time of the test; 

alternative screening procedures were tested only if inspectors 

coincidentally conducted a test at a screening station while one of the 

procedures was in use. Office of Inspections officials stated that they did 

TSA Has Not Tested the 

Operational Security 

Effectiveness of 

Alternative Screening 

Procedures through Covert 

Testing 

 27GAO, Aviation Security: Screener Training and Performance Measurement 

Strengthened, but More Work Remains, GAO-05-457 (Washington, D.C.: May 2, 2005). 

28TSA classifies the over 400 airports in the United States into one of five categories—X, I,

II, III, and IV. Generally, category X airports have the largest number of passenger 

boardings and category IV airports have the smallest number. 

Page 19 GAO-06-869 Aviation Security
not schedule tests of alternative screening procedures because their 

resources were dedicated to conducting testing on standard screening 

procedures. Furthermore, the officials stated that since covert testing 

visits are planned in advance of the tests and the need to use alternative 

screening procedures is not always known in advance, it would be 

logistically difficult to plan a covert testing visit to coincide with an 

airport’s use of alternative screening procedures because of airports’ 

intermittent and often short-term use of the procedures. While it may be 

logistically difficult to conduct national covert testing on alternative 

screening procedures, PMIS data on which airports most frequently use 

the procedures and the reasons for the usage could provide the Office of 

Inspections with information to select airports for covert testing as part of 

the risk-based approach to covert testing that it is developing. 

In addition to its national covert testing program, in March 2005, TSA also

began an airport-based local covert testing program to determine if TSA 

checked baggage TSOs can detect a simulated improvised explosive 

device that is hidden in a test bag. Participation in this program is at the 

discretion of the FSD. FSD staff test screening at EDS stations by placing

simulant explosives in baggage and surreptitiously running the bags 

through the machines. According to TSA, between March 2005 and 

February 2006, 2,526 local tests of EDS screening were conducted at 

108 airports. When we asked TSA headquarters officials in charge of the 

local covert testing program about the feasibility and usefulness of testing 

the use of alternative screening procedures, they stated that they had not 

previously considered testing the procedures through the local covert 

testing program. These officials also cited challenges in conducting such 

testing, including the difficulty in predicting the need to use the 

procedures and the lack of available federal staff to conduct the testing, 

particularly at smaller airports. Because FSDs and their staffs authorize 

and initiate the use of alternative screening procedures, they could 

schedule some of their ongoing local covert testing for checked baggage

screening to coincide with the use of these procedures. In not testing the 

alternative screening procedures through national or local covert testing, 

TSA is not collecting data that could provide useful information on how to 

improve the security effectiveness of these procedures in detecting 

explosives. 

Page 20 GAO-06-869 Aviation Security
TSA reported using both standard and alternative screening procedures in 

PMIS but could not identify the percentage of all checked baggage

screening using EDS and ETD with standard or alternative screening 

procedures. TSA cannot identify the percentage of usage of standard or 

alternative screening procedures because for standard screening 

procedures, PMIS contains data on the number of bags screened, whereas 

for alternative screening procedures it contains data on the number of 

occasions and hours of use.29 However, TSA officials estimated that a high

percentage of checked baggage is screened using EDS and ETD machines 

with standard screening procedures30 and a low percentage is screened 

using alternative screening procedures.31 TSA determined that the number 

of bags screened using EDS and ETD with standard screening procedures

The Full Extent of the 

Usage of Alternative 

Screening Procedures 

Is Not Known, and 

Internal Controls for 

Monitoring the Usage 

of Baggage Screening 

Procedures Could Be 

Improved 

TSA Does Not Collect 

Consistent Data on the Use 

of Standard and 

Alternative Screening 

Procedures to Enable an 

Accurate Determination of 

the Full Extent of Their 

Use 

 29Although FSDs and their staffs are not required to report the number of bags screened

with alternative screening procedures into PMIS, some FSDs and staff from airports that 

reported using alternative screening procedures reported this information in comment 

fields on occurrences of use of alternative screening procedures between October 2004 and 

September 2005. The number of FSDs and the number of occurrences have been

determined to be sensitive security information. 

30TSA does not require airports to report information on the number of bags screened using

alternative screening procedures. To derive an estimate of use of alternative screening 

procedures across the system, TSA used alternative screening procedures baggage counts

only from those airports that voluntarily reported the information in order to calculate the 

average number of bags screened per hour. TSA then used this calculation of the average

bags per hour and the total number of screening hours using the procedures to make this

estimate. Because TSA did not have baggage counts for all of the occurrences of alternative

screening procedures, this estimate may be inaccurate. 

31TSA determined that its estimate of the use of alternative screening procedures is 

sensitive security information. 

Page 21 GAO-06-869 Aviation Security
between October 2004 and September 2005 as well as data on the use of 

alternative screening procedures reported into PMIS during this same 

period are sensitive security information. 

TSA established internal controls to monitor and track the usage of 

standard and alternative screening procedures, but has not adequately 

implemented some of these controls. An internal control is an integral 

component of an organization’s management and is designed to provide 

reasonable assurance that agencies achieve effectiveness and efficiency of

operations and compliance with applicable laws and regulations. The 

Comptroller General’s Standards for Internal Controls require that 

transactions and events be completely and accurately recorded in order to

ensure that information is available for management to guide operations 

and make decisions.32 While TSA has established internal controls to 

monitor and track use of baggage screening procedures, such as requiring

FSDs and their designates to report the use of alternative screening 

procedures into PMIS and to call TSA headquarters for permission to use 

the procedures for more than 2 hours, some of the controls have not been

adequately implemented because events have not been completely and 

accurately recorded. Consequently, TSA does not have complete 

information on the extent of the use of alternative screening procedures 

that would be helpful for TSA management in making decisions on actions

to minimize the need to use alternative screening procedures at airports, 

such as deploying screening equipment. 

Information that FSDs and their staffs report in PMIS regarding the 

number of bags screened using ETD machines may not be accurate 

because of the way in which the number of bags screened is estimated. 

While EDS machines automatically count each bag screened, ETD 

machines count each swab analyzed, rather than each bag screened. TSA 

uses this count of analyses to estimate the number of bags screened using 

ETD. The number of analyses for a bag screened using ETD may vary 

depending on how many times the machine alarms during the screening 

process and other factors, which may lead to overreporting of baggage 

screened. TSA officials stated that they are aware of these discrepancies

and are working to improve counting of baggage screened using ETD.33

TSA Established Internal 

Controls to Monitor the 

Usage of Standard and 

Alternative Screening 

Procedures, but Some 

Controls Have Not Been 

Adequately Implemented 

Recording of ETD Baggage 

Screening in PMIS 

 32GAO, Standards for Internal Control in the Federal Government, GAO/AIMD-00-21.3.1

(Washington, D.C.: November 1999). 

33TSA determined that the other factors that may influence the number of analyses 

completed for a bag screened using ETD are sensitive security information. 

Page 22 GAO-06-869 Aviation Security
Improved counting of bags would provide TSA management with better 

information to use in making decisions related to its baggage screening 

operations, including where to deploy screening equipment. 

FSDs and their staffs did not always completely and accurately record 

information in PMIS on the use of various alternative screening 

procedures. On the basis of our review of PMIS data from October 2004 

through September 2005, we found that FSDs and their designates did not 

always accurately report the occurrences when a particular baggage 

screening procedure was used. For example, some of the airports that 

reported using alternative screening procedures voluntarily reported in a 

PMIS comments field that they used the procedures intermittently over the 

course of several hours, even though in PMIS they reported only one 

occurrence that lasted several hours.34 FSD staff at one of these airports 

reported in PMIS one occurrence of using alternative screening 

procedures for 15.5 hours straight but reported in the comments field that

the procedures were used during 24 different occurrences during the 

15.5 hours. According to TSA guidance, these data should have been 

recorded as 24 separate occurrences in the PMIS database, not simply 

noted in the comments field. TSA officials stated that they were aware that

many airports were reporting the use of alternative screening procedures 

for extended periods of time rather than recording each time the use of the 

procedures was started and stopped within the reported time. In May 2005, 

the TSA Assistant Administrator for Aviation Programs sent a memo to 

FSDs noting that the start and stop time of each individual use of an 

alternative screening procedure at each screening station should be 

reported into PMIS. In our analysis of PMIS data from May 2005 through 

September 2005, subsequent to the issuance of this memo, some of the 

airports continued to report intermittent use of alternative screening 

procedures in the comments fields. 

The design of PMIS also contributed to incomplete and inaccurate 

recording of information because it does not allow FSDs and their 

designates to report two or more alternative screening procedures used 

during the same occurrence. TSA officials have instructed FSDs and their 

designates to record the alternative screening procedure that is used the 

most during the occurrence. One airport voluntarily reported in the PMIS 

Recording Occurrences of 

Alternative Screening 

Procedures 

 34The comments field is a PMIS database field used to add descriptive data on the

alternative screening procedures occurrence. TSA determined that the exact number of 

airports that voluntarily reported intermittent use of alternative screening procedures in 

the comments field is sensitive security information. 

Page 23 GAO-06-869 Aviation Security
comments field that it used three alternative screening procedures 

throughout the occurrence. However, the PMIS database only allowed 

reporting of the use of one of the procedures during this time. Because of

these reporting limitations, TSA managers do not receive complete 

information on how often or for how long the various alternative screening 

procedures are actually used—information that could affect their 

decisions on what actions to take to minimize the need to use alternative

screening procedures at airports. 

Another factor that could contribute to incomplete and inaccurate 

reporting of alternative screening procedures in PMIS is that although 

FSDs and their staffs are required to report every occurrence of the 

procedures in PMIS, they may not have always done so. Until August 2005, 

when this requirement was eliminated, FSDs and their staffs were required 

to report to the Transportation Security Operations Center—TSA’s 

command, control, communications and intelligence center—whenever 

they were about to begin using alternative screening procedures or to 

switch back to standard EDS or ETD screening after using alternative 

screening procedures.35 While TSA officials stated that they did not keep 

formal records of the calls, they kept what TSA termed “informal notes” on 

sheets that included times when the use of the alternative screening 

procedures began and ended and the type of procedure used. When we 

compared a select number36 of these sheets completed between February 

and March 2005 to PMIS reporting for the same period, we found that 

21 percent of the occurrences of use of alternative screening procedures 

recorded on the sheets were not recorded into PMIS as required by TSA’s

standard operating procedures.37 Inaccurate reporting on the frequency of 

use of alternative screening procedures may hinder management decision 

making on how best to minimize airport need to use these procedures. 

While TSA’s standard operating procedures require FSDs or their 

designates to call headquarters for permission to use alternative screening 

procedures that are used for more than 2 hours in order to ensure that the 

Permission to Use Alternative 

Screening Procedures for More 

than 2 Hours 

 35TSA officials stated that they eliminated this requirement because headquarters could get 

information on use of alternative screening procedures through PMIS. 

36TSA classified the number of sheets that we reviewed as sensitive security information. 

37We selected sheets to analyze based on the completeness of the information contained on 

the sheets. Each sheet selected had a date, an airport code or name, a beginning and end 

time of use of alternative screening procedures, type of alternative screening procedure 

used, and reason for using the alternative screening procedure. 

Page 24 GAO-06-869 Aviation Security
procedures are used only for short-term, special circumstances, TSA does 

not require headquarters to maintain a record of these calls. Because these 

calls are not recorded, TSA management is not able to ensure that the 

requirement in the standard operating procedures is being followed. 

Recording these calls would enable TSA to compare the records to the 

hours of use of alternative screening procedures data maintained in PMIS. 

This comparison would provide TSA with information to help provide 

reasonable assurance that FSDs and their staffs are complying with the 

standard operating procedures’ requirement to call for permission to 

exceed 2 hours’ use of the procedures. TSA headquarters officials stated

that there had not been any instances in which airports were denied 

permission to exceed 2 hours’ use of alternative screening procedures. 

However, without records of the calls, we were not able to verify that 

permission was granted for the occurrences that exceeded 2 hours.38

TSA has taken steps to reduce airports’ need to rely on the use of 

alternative baggage screening procedures and is working to minimize the 

need to use these procedures. According to our review of PMIS data, the 

use of alternative screening procedures between October 2004 and 

September 2005—measured in terms of the total hours these procedures 

were employed—initially increased and then declined. TSA attributed the 

reported overall decline in the usage of alternative screening procedures 

TSA Has Taken Action 

to Reduce the Need to 

Use Alternative 

Screening 

Procedures, but Has 

Not Implemented 

Performance 

Measures or Targets 

TSA Has Taken Steps to 

Reduce the Need to Use 

Alternative Screening 

Procedures at Airports 

 38TSA classified the number of occurrences that were more than 2 hours as sensitive 

security information. 

Page 25 GAO-06-869 Aviation Security
in part to improved coordination among FSDs, airlines, and local 

organizations. According to TSA officials, this coordination helps FSDs 

and their staffs anticipate surges in passenger traffic so that they can 

adequately staff screening stations. In our structured interviews with FSDs 

and their staffs responsible for 29 airports, several FSDs also cited the 

importance of coordination with local organizations and how this reduced 

their need to use alternative screening procedures. For example, the FSD

for one airport said that he coordinated with local summer camps to have 

campers’ baggage screened the day before their flights to reduce the 

amount of baggage that has to be screened when campers arrive at the 

airport. The FSD for another airport communicated with cruise ship 

management about the scheduling of cruises in order to anticipate any 

surges in passenger traffic that may have created the need to use 

alternative screening procedures. 

TSA officials have also taken action to reduce airports’ need to use 

alternative screening procedures through the use of “optimization team” 

visits to airports. These visits are conducted at the request of TSA senior 

leadership or an FSD with the goal to observe screening operations and 

maximize efficiencies by applying practices learned at other airports. 

According to TSA officials, recurring use of alternative screening 

procedures triggered some of the optimization team visits TSA has 

conducted, and the optimization team visits may have led to a reduction in

the number of occasions in which these procedures needed to be used.39

For example, on May 18-19, 2005, an optimization team visited one airport 

and recommended procuring one ETD machine and changing the location

of another to reduce the airport’s need to use alternative screening 

procedures. On July 6-7, 2005, another optimization team visited another 

airport. The team suggested reconfiguring EDS machines at the airport’s 

screening stations, which resulted in an increase in baggage throughput 

from 120 to 150 bags per hour. At both of these airports, alternative 

screening procedures were used more frequently prior to the optimization 

team visit than they were after the visit. 

TSA officials also stated that as additional equipment is deployed and

enhanced to enable TSA to increase checked baggage screening 

throughputs—bags screened per hour—TSA will be in a better position to 

 39The optimization visits are also used to improve the design of passenger and baggage 

checkpoints, validate the TSO staffing model at the airport, evaluate staffing and

scheduling practices, and determine compliance with the standard operating procedures. 

Page 26 GAO-06-869 Aviation Security
reduce the need for use of alternative screening procedures. We reported

in March 2005 that as of June 2004, TSA had deployed 1,228 EDS 

machines.40 Between June 2004 and June 2006, TSA had deployed 

399 additional EDS machines in both in-line (integrated into the airport 

baggage system) and stand-alone (in airport lobbies or baggage makeup 

areas) configurations. EDS machines in an in-line configuration are able to

screen up to 500 bags per hour, as compared to EDS machines in a standalone configuration that screen between 80 and 180 bags per hour. The 

superior efficiency of screening with in-line EDS compared to screening 

with stand-alone EDS may have been a factor in reducing the need to use

alternative screening procedures at airports where in-line systems were 

installed. TSA reported that, as of June 2006, 25 airports had operational 

in-line EDS systems and an additional 24 airports had in-line systems 

under construction. Although in-line EDS systems can create 

improvements in operational efficiencies of an airport’s checked baggage

screening system, baggage volumes that exceed the system’s capacity and

equipment breakdowns still sometimes occur, necessitating the use of 

alternative screening procedures. For example, some of the airports that 

have installed airportwide in-line systems reported using alternative 

screening procedures because of equipment failures and high passenger 

and baggage volumes after their systems were operational.41 Since standalone EDS machines screen between 80 and 180 bags per hour compared 

to ETD machines, which allow for screening of 36 bags per hour, 

additional stand-alone EDS machines also may have helped the airports 

where they were installed to screen baggage with standard screening 

procedures rather than alternative screening procedures. Additionally, in

May 2005, TSA certified software and hardware upgrades for 519 out of 

1,322 EDS machines, which are used in both in-line and stand-alone 

configurations. These upgrades are being tested in a pilot program. TSA 

officials anticipate that the upgrades could lead to increased baggage 

throughput for the machines, which could further reduce need to use 

alternative screening procedures. 

Installation of in-line EDS systems at airports that currently use standalone EDS and ETD for primary screening has further potential to reduce 

 40GAO-05-365. 

41Each of the airports’ in-line systems became operational on a different date. The number 

of airports that reported using alternative screening procedures due to equipment failures

and high passenger and baggage volumes after their systems were operational has been

determined to be sensitive security information. 

Page 27 GAO-06-869 Aviation Security
the need for alternative screening procedures to be used at these airports. 

In March 2005, we reported that TSA had estimated that in-line checked 

baggage systems would reduce by 78 percent the number of baggage TSOs

and supervisors required to screen checked baggage at nine airports that 

had signed agreements to develop the systems.42 Under the congressionally 

imposed 45,000 TSO full-time-equivalent limit, when staff requirements are 

reduced at one airport through increased efficiencies, full-time equivalent 

positions will become available to address TSO shortages at other 

airports.43 TSA’s February 2006 checked baggage strategic planning 

framework included a prioritization of which additional airports should 

receive funding for in-line systems and a description of how stand-alone 

EDS machines from those airports should be redistributed to other 

airports.44 In the framework, TSA also reported that many of the initial inline systems had produced a level of TSO labor savings insufficient to 

offset up-front capital costs of constructing the systems. According to 

TSA, the facility and baggage handling system modifications have been 

higher than expected at the nine airports that have signed agreements to 

fund the systems. TSA stated that the keys to reducing future costs are 

establishing guidelines outlining best practices and a set of efficient design

choices and using newer EDS technology that best matches each optimally 

scaled design solution. In February 2006, TSA reported that recent 

improvements in the design of the in-line EDS checked baggage screening 

systems and the EDS screening technology now offer the opportunity for 

higher-performance and lower-cost screening systems. The final strategic

plan will include the results of TSA’s cost sharing study that it is currently 

conducting in consultation with airport operators, airlines, and other key 

stakeholders to identify ways to fund in-line EDS systems.45 After in-line 

 42GAO-05-365. 

43Section 4023 of the Intelligence Reform and Terrorism Prevention Act of 2004 requires 

TSA to develop and submit to the appropriate congressional committees, standards for 

determining aviation security staffing at commercial airports no later than 90 days after

December 17, 2004, the date of the act’s enactment, and GAO to conduct an analysis of 

these standards. These standards were submitted to Congress on June 22, 2005, and GAO is

currently reviewing these standards. 

44The details of the strategic planning framework for the checked baggage screening 

program constitute sensitive security information. 

45Section 4019(d) of the Intelligence Reform and Terrorism Prevention Act of 2004 requires 

TSA to complete a cost-sharing study in collaboration with industry stakeholders to review

the benefits and cost of in-line checked baggage screening systems, innovative financing

approaches, formulas for cost sharing between different government entities and the 

private sector, and potential cost-saving approaches. 

Page 28 GAO-06-869 Aviation Security
EDS systems are installed and staffing reductions are achieved, 

redistributing the TSO positions to other airports with staffing shortages 

may reduce airport need to use alternative screening procedures. 

Technology developments may also help TSA to reduce the use of 

alternative screening procedures. In March 2005, we reported that TSA 

was working to develop a computer-aided tomography explosives 

detection system that is smaller and lighter than systems currently 

deployed in airport lobbies and that the new system was intended to 

replace systems currently in use, including larger and heavier EDS 

machines and ETD equipment.46 The smaller size of the system would 

create opportunities for TSA to transfer screening operations to other 

locations, such as airport check-in counters. The machine would also be 

an option for airports that currently rely on ETD machines since it would

be cheaper than other certified machines and it would have higher 

baggage throughput than screening using ETD machines, potentially 

reducing the need to use alternative screening procedures at airports 

where it is installed. In March 2005, TSA began to pilot this machine at 

three airports. At one of these pilot airports, the FSD stated that he 

anticipates that the smaller EDS machine will reduce staffing needs, 

reduce workers compensation claims, and ultimately enable the airport to 

incorporate the machines in-line behind the ticket counters. TSA reported 

that the machine achieved throughput rates of up to 80 bags per hour, 

higher than the throughput rate of up to 36 bags per hour for an ETD 

operated by one TSO or up to 72 bags per hour for an ETD operated by 

two TSOs. In September 2005, TSA entered into a $24.8 million contract to

purchase 72 of these machines that will be installed at 24 airports. 

While TSA data indicate that the use of alternative screening procedures is 

declining, TSA reported in its February 2006 framework that at some 

airports alternative screening procedures will increasingly be used 

because of rising passenger traffic. TSA has projected that the number of 

originating domestic and international passengers will rise by about 

127 million passengers over current levels by 2010. If TSA’s current 

estimate of an average of 0.76 checked bags per passenger were to remain 

constant through 2010, TSA would be screening about 96 million more 

bags than it now screens. This could increase airports’ need to rely on 

alternative screening procedures in the future in the absence of additional

or more efficient EDS machines. TSA headquarters officials stated that 

 46GAO-05-365. 

Page 29 GAO-06-869 Aviation Security
while TSA is working to minimize the need to use alternative screening 

procedures, it intends to maintain the procedures as part of its standard 

operating procedures so that FSDs will have options to respond to events 

such as unforeseen equipment failures, surges in passenger traffic, and

weather-related incidents such as hurricanes. Additionally, some of the 

FSDs that we interviewed stated that they anticipate continuing to need to

use alternative screening procedures because of screening capacity limits 

and rising passenger volume, and some of these FSDs anticipated 

increasing their use of the procedures as their airport passenger traffic 

rises because of limitations in the physical layout of their airports that 

contribute to overcrowding.47

Although TSA is working to minimize the need to use alternative screening 

procedures at airports, it has not established performance measures or 

targets related to the use of these procedures. The Government 

Performance and Results Act of 1993 provides, among other things, that 

federal agencies establish program performance measures, including the 

assessment of relevant outputs and outcomes of measures.48 Performance 

measures are meant to cover key aspects of performance and help 

decision makers to assess program accomplishments and improve 

program performance. A performance target is a desired level of 

performance expressed as a tangible, measurable objective, against which 

actual achievement will be compared. By analyzing the gap between target 

and actual levels of performance, management can target those processes 

that are most in need of improvement, set improvement goals, and identify

appropriate process improvements or other actions. 

TSA has established four performance measures for the checked baggage

screening program. Three of these measures make up TSA’s checked 

baggage screening performance index. This index measures the overall

performance of the system through a composite of indicators that are 

derived by combining specific performance measures related to checked 

TSA Has Not Established 

Performance Measures or 

Targets Related to the Use 

of Alternative Screening 

Procedures 

 47TSA determined that the exact number of FSDs that anticipate continued or increased use

of alternative screening procedures is sensitive security information. 

48According to the Government Performance and Results Act, the Office of Management 

and Budget, and GAO, outcomes assess actual results as compared with the intended 

results that occur from carrying out a program or activity. Outcomes are the results of a

program or activity. For further information, see GAO, Results-Oriented Government: 

GPRA Has Established a Solid Foundation for Achieving Greater Results, GAO-04-38 

(Washington, D.C.: Mar. 10, 2004). 

Page 30 GAO-06-869 Aviation Security
baggage screening. Specifically, this index measures the effectiveness of 

screening systems through machine probability of detection and covert 

testing results, efficiency through a calculation of dollars spent per bag 

screened, and customer complaints at both airports and TSA’s national 

call center. TSA considers the final performance measure—compliance 

with the ATSA requirement to screen all checked baggage using explosive 

detection systems (EDS and ETD)—to be obsolete since it reported all 

airports as capable of screening with EDS or ETD in January 2005. The use 

of alternative screening procedures is not included in the index, nor does

TSA have stand-alone measures or targets for the use of alternative 

screening procedures. 

TSA officials stated that they did not want to implement performance 

measures or targets for alternative screening procedures because they are

already working to minimize the need to use the procedures at airports. 

However, TSA officials also acknowledged that they will continue to rely 

on alternative screening procedures because of unforeseen circumstances 

such as high baggage volumes or weather-related incidents. By creating a 

performance measure for the use of alternative screening procedures as 

part of the checked baggage screening index or as a stand-alone measure, 

TSA could gauge whether it is making progress toward minimizing the 

need to use these procedures at airports and have more complete 

information on how well the overall checked baggage screening system is 

performing. Furthermore, performance targets for the use of alternative 

screening procedures would provide an indicator of how much risk TSA is 

willing to accept in using these procedures, and TSA’s monitoring of this 

indicator would identify when it has exceeded the level of risk that it has 

determined is acceptable. For example, if TSA were to determine the 

percentage of checked baggage that should be screened using alternative 

screening procedures, and if its performance data showed that it was 

currently screening a higher percentage than the target, TSA would be able 

to decide whether to take steps to bring the use of these procedures into

line with its desired level of use. 

Finally, the extent to which performance measures and targets will assist 

TSA in minimizing the need to use these procedures at airports is 

dependent upon the accuracy and completeness of the reporting of 

alternative screening procedures in PMIS, including the percentage of bags

screened using the procedures, as previously discussed. 

It has been over 4 years since Congress issued the mandate for TSA to 

screen all checked baggage at commercial airports using explosive Conclusions 

Page 31 GAO-06-869 Aviation Security
detection systems. During this time, TSA has deployed EDS or ETD 

machines at more than 400 commercial airports and reported achieving 

the capability to screen 100 percent of checked baggage using these 

machines. As part of this effort, TSA developed standard and alternative

checked baggage screening procedures. While TSA acknowledges that 

screening with alternative screening procedures is less effective than 

screening with standard screening procedures, it has also recognized the 

need for continued use of alternative screening procedures because of 

high passenger and baggage volumes resulting from unpredictable and

unforeseen circumstances, such as equipment breakdowns and unusual 

weather events. Given TSA’s plans to continue to use alternative screening 

procedures and the trade-offs in security effectiveness involved in their 

use, it will be important for TSA to test the effectiveness of these 

procedures in an operating environment. One such way for TSA to test the 

security effectiveness of the various alternative screening procedures is 

through the covert testing conducted by the Office of Inspections. While 

we recognize the logistical challenges that the Office of Inspections faces 

in conducting checked baggage covert testing on alternative screening 

procedures, using PMIS data on the use of these procedures—including 

data on the airports that use the procedures the most frequently or for 

extended periods of time—could help the Office of Inspections in 

selecting airports for testing as part of the risk-based approach to covert 

testing that it is currently developing. By not assessing alternative 

screening procedures through national or local covert testing, TSA is 

missing an opportunity to gather information to help determine the 

security effectiveness of alternative screening procedures in an

operational setting. 

Additionally, TSA headquarters has established internal controls to 

monitor and track the use of alternative screening procedures at airports 

and has taken steps to improve reporting of these procedures in the PMIS 

database. However, without strengthening its controls, such as providing a 

means for measuring the number of bags screened using alternative 

screening procedures and enabling TSA airport staff to report the 

concurrent use of more than one alternative screening procedure, TSA 

lacks reasonable assurance that it has complete and accurate information 

on the use of these procedures. 

Furthermore, TSA has taken steps to reduce the need to use alternative

screening procedures at airports, but does not expect to eliminate the use

of these procedures. Increasing air travel and TSA’s effort to operate 

within or below the current 45,000 TSO full-time-equivalent limit could add 

to the need for alternative screening procedures, unless more or more 

Page 32 GAO-06-869 Aviation Security
efficient EDS machines are deployed. Given TSA’s continuing use of the 

procedures, performance measures and targets would provide TSA and 

Congress with objective information to assess TSA’s progress in 

minimizing the need to use the procedures at airports, and would help 

inform TSA decision making on whether and when mitigating steps are 

needed to achieve its desired level of use. 

To help inform TSA of the security effectiveness of alternative screening 

procedures in an operational setting, and to help TSA strengthen its 

monitoring of the use of alternative screening procedures, we recommend 

that the Secretary of the Department of Homeland Security direct the 

Assistant Secretary, Transportation Security Administration, to take the 

following four actions: 

Recommendations for 

Executive Action 

• Use PMIS data on use of alternative screening procedures in determining 

at which airports to conduct covert testing and when to conduct testing at 

these airports as part of the Office of Inspections’ new risk-based 

approach to covert testing. 

• Conduct local covert testing of alternative screening procedures to 

determine whether checked baggage TSOs can detect simulated 

improvised explosives when using these procedures. 

• Strengthen the monitoring and tracking of the use of alternative screening 

procedures to help determine the progress the agency is making in 

minimizing its need to use these procedures. This effort would include 

continuing to address reporting problems in the PMIS database system, 

keeping a record of calls requesting permission to exceed 2 hours’ use of 

the procedures, and providing a means for measuring the use of 

alternative screening procedures compared to the use of standard 

procedures, such as counting baggage screened with alternative screening 

procedures. 

• Develop performance measures and performance targets for the use of 

alternative screening procedures in checked baggage screening, perhaps 

as part of the checked baggage screening program performance index, to

help TSA measure its progress in working toward minimizing the need to 

use alternative screening procedures at airports and to have more 

complete information on the overall performance of the checked baggage 

screening system. 

Page 33 GAO-06-869 Aviation Security
We provided a draft of this report to DHS for review and comment. On 

July 25, 2006, we received written comments on the draft report, which are 

reproduced in full in appendix II. DHS concurred with our findings and 

recommendations and stated that the report will help strengthen TSA’s 

management of checked baggage screening operations. 

Regarding our recommendation that TSA use Performance Management 

Information System data on the use of alternative screening procedures in 

determining at which airports to conduct covert testing and when to 

conduct testing at these airports, DHS concurred and stated that TSA’s 

Office of Inspections will consider PMIS information on alternative 

screening procedures as part of its new risk-based approach to covert 

testing and will develop new checked baggage screening testing protocols. 

Concerning our recommendation that TSA conduct local covert testing of 

alternative screening procedures, DHS concurred and stated that TSA is 

currently modifying its local covert testing program to strengthen the 

program and expects that these modifications will better prepare TSOs to 

detect simulated improvised explosives. We are pleased that TSA is 

making efforts to strengthen its local covert testing program. We continue 

to believe that testing of alternative screening procedures would provide 

TSA with an opportunity to gather information to help identify and 

improve the security effectiveness of alternative screening procedures in 

an operational setting. 

DHS concurred with our recommendation to strengthen the monitoring 

and tracking of the use of alternative screening procedures to help 

determine the progress the agency is making in minimizing its need to use 

the procedures. In response to our recommendation that TSA address 

reporting problems in its PMIS database system, DHS stated that PMIS has 

been enhanced with both functionality and data quality-related processes 

to ensure data reliability. According to TSA, the system alerts the user 

when a data field is filled in with a value that falls outside the operational 

norms for a particular airport. Additionally, according to TSA, PMIS 

training and functionality reviews occur on a regular basis and user 

manuals and best practices are updated consistently. While these efforts 

should help improve the data reliability of PMIS, they will not fully address 

the reporting problems highlighted in our report. Specifically, the steps 

TSA has taken do not address inaccurate counts of baggage screened 

resulting from TSA’s method for estimating the number of bags screened 

with ETD using standard screening procedures or inaccurate reporting of 

occurrences when a particular alternative screening procedure is used. 

Without addressing these reporting problems, TSA will continue to lack 

Agency Comments 

and Our Evaluation 

Page 34 GAO-06-869 Aviation Security
reasonable assurance that it has complete and accurate information on the 

use of these procedures. 

In response to our recommendation on keeping a record of calls 

requesting permission to exceed 2 hours use of the procedures, DHS 

stated that because the amount of time that alternative screening 

procedures are used is recorded in PMIS, there is no further 

documentation required for exceeding the 2 hour threshold. However, 

while documentation is entered into PMIS on the amount of time the 

procedures are used, recording the length of time that the procedures are 

used does not allow TSA to verify that FSDs are actually requesting 

permission to use the procedures for more than 2 hours as required. In 

response to our recommendation on providing a means for measuring the 

use of alternative screening procedures compared to the use of standard 

procedures, such as counting baggage screened with alternative screening 

procedures, DHS stated that TSA will evaluate the necessity of requiring 

the recording of the number of bags screened by alternative screening 

procedures, and if it finds it to be a useful metric, it will require FSDs to 

include the number of bags in their report in PMIS. We are encouraged 

that TSA will undertake this evaluation, as we believe that it will allow 

TSA to have more assurance that it has complete and accurate information 

on the use of these procedures. 

In response to our recommendation on developing performance measures 

and targets for the use of alternative screening procedures, DHS 

concurred and stated that TSA is currently meeting the intent of this 

recommendation by monitoring and tracking the use of alternative 

screening procedures through PMIS. DHS stated that using this system has 

assisted TSA in identifying areas for improvement nationwide and 

addressing local issues to minimize the need for alternative screening 

procedures. DHS also stated that TSA intends to continue monitoring and 

tracking the use of alternative screening procedures and to implement the 

recommendations in this report for refining the data and evaluating the 

need to make adjustments based on the current performance level. While 

we support TSA’s efforts to ensure the use of alternative screening 

procedures is accurately reported in PMIS, given the security effectiveness 

trade-offs associated with alternative screening procedures, we do not 

believe that tracking the use of the procedures with PMIS is sufficient to 

provide congressional and other decision makers with an indication of the 

progress the agency expects to make in minimizing the need to use the 

procedures at airports. Performance measures and targets would provide 

this information and would help to reinforce accountability and to ensure 

that managers focus on the results they are striving to achieve regarding

Page 35 GAO-06-869 Aviation Security
minimizing the use of alternative screening procedures in their day-to-day

activities. 

We will send copies of the report to the Secretary of the Department of 

Homeland Security; the Assistant Secretary, TSA; and interested 

congressional committees as appropriate. We will also make copies 

available to others on request. In addition, the report will be available at 

no charge on GAO’s Web site at http://www.gao.gov. 

If you or your staff have any questions about this report, please contact me 

at (202) 512-3404 or berrickc@gao.gov. Contact points for our Offices of 

Congressional Relations and Public Affairs may be found on the last page 

of this report. GAO staff that made major contributions to this report are 

listed in appendix III. 

Sincerely yours, 

Cathleen A. Berrick 

Director, Homeland Security and 

 Justice Issues 

Page 36 GAO-06-869 Aviation Security
Appendix I: Objectives, Scope, and 

Methodology 

Page 37 GAO-06-869 Aviation Security

Appendix I: Objectives, Scope, and 

Methodology 

To assess the Transportation Security Administration’s (TSA) efforts to 

screen all checked baggage using explosive detection systems (EDS) and 

explosive trace detection machines (ETD), we addressed the following 

questions: (1) How did TSA prioritize the use of standard and alternative 

checked baggage screening procedures and what security effectiveness 

trade-offs and operational efficiencies has TSA identified in using these 

procedures to screen checked baggage for explosives? (2) To what extent 

has TSA used standard and alternative screening procedures to screen 

checked baggage for explosives and how does TSA ensure that standard 

screening procedures are used whenever possible? (3) What steps has TSA 

taken to reduce airports’ need to use alternative screening procedures and 

to establish performance measures and targets for the use of the 

procedures? 

To assess how TSA prioritized the use of checked baggage screening 

procedures and to assess the trade-offs in security effectiveness and 

operational efficiencies associated with various baggage screening 

procedures, we analyzed TSA’s standard operating procedures for using 

these procedures. We also obtained and analyzed relevant legislation and 

conducted a literature search to obtain information on screening 

procedures, technologies, and related aviation trends. This search 

identified various TSA reports, Department of Homeland Security 

Inspector General reports, and aviation industry reports. We also reviewed 

studies from the TSA Transportation Security Laboratory regarding 

checked baggage screening. We interviewed officials from various TSA 

offices, including the Chief Technologist’s Office, Aviation Programs, the 

Transportation Security Operations Center, the Transportation Security 

Laboratory, Chief Operating Officer’s Office, and Office of Planning to 

learn about checked baggage screening procedures and how they were 

given relative priority. We also interviewed officials from air carriers, 

explosive detection systems equipment manufacturers, and an airport 

industry association to obtain information regarding TSA’s checked 

baggage screening procedures. We assessed the results from 

unannounced, undercover covert testing of checked baggage screening 

operations conducted by TSA’s Office of Inspections and questioned TSA 

officials about the procedures used to ensure the reliability of the covert 

test data. On the basis of their answers, we believe that the covert test data

are sufficiently reliable for the purposes of our review. We also reviewed 

results of unannounced, undercover covert testing of checked baggage 

screening operations conducted at airports by Federal Security Directors 

(FSD) and their staffs and collected as part of TSA’s Screener Training 

Exercises and Assessments program. After reviewing documentation from 

TSA, we found the data from the Screener Training Exercises and 
Appendix I: Objectives, Scope, and 

Methodology 

Assessments program were sufficiently reliable for the purposes of our 

review. 

To assess the extent to which TSA has used standard and alternative 

screening procedures to screen checked baggage and how TSA ensures 

that standard checked baggage screening procedures are used whenever 

possible, we reviewed and analyzed TSA’s Performance Management 

Information System (PMIS) database, which contains information on 

baggage screening operations and the use of alternative screening 

procedures. We found several issues with these data, including, in some 

cases, multiple occurrences of the use of alternative screening procedures 

recorded as one occurrence and also, in some cases, more than one 

procedure being used during an occurrence but the occurrence was 

entered into the database as only one procedure because of the 

constraints of the database. When we interviewed TSA officials about 

these data reliability issues, officials acknowledged that airports may have 

inaccurately reported some occurrences of the use of alternative screening

procedures. However, the officials stated that they were working to 

correct the reporting problems and consider the data generally reliable. On 

the basis of these discussions and our review of the database, we found 

the data to be sufficiently reliable for the purposes of this report, since the 

data provide overall trends in the use of the procedures. To determine 

what controls are in place to track and report the use of baggage screening

procedures, we analyzed the PMIS database and the PMIS user guide. We

also analyzed TSA’s operating procedures for checked baggage and policy 

guidance and compared TSA’s procedures for ensuring that airports 

correctly report the use of alternative screening procedures to the 

Comptroller General’s Standards for Internal Controls in the Federal 

Government. We also interviewed officials from TSA’s Office of Planning, 

Chief Operating Office, Transportation Security Operations Center, and 

Inspections offices concerning checked baggage screening procedures. 

To assess the steps TSA has taken to reduce airports’ need to use 

alternative screening procedures and the measures and targets TSA has set 

for alternative screening procedures, we analyzed TSA’s PMIS data and its 

standard operating procedures for checked baggage screening and TSA’s 

inventory of explosive detection systems. We found discrepancies in the 

inventory data of explosive detection systems and worked with TSA to 

resolve the discrepancies. TSA also completed a reconciliation of the 

inventory database with data collected manually by TSA officials. We also

analyzed documentation from the TSA Transportation Security Operations

Center and interviewed TSA officials from the Chief Operating Officer’s 

Office, Office of Planning, the Office of Assistant Secretary, and Chief 

Page 38 GAO-06-869 Aviation Security
Appendix I: Objectives, Scope, and 

Methodology 

Technology Office. Additionally, we examined TSA’s checked baggage 

performance measures and targets in the context of the Government 

Performance and Results Act of 1993 (GPRA) requirements. 

In addressing these objectives, we conducted site visits at nine airports—

three category X, one category I, four category II, and one category IV 

airport. We chose these airports based on one or more of the following 

factors: use of alternative screening procedures at the airport as reported 

in PMIS, testing of screening equipment at the airport, proximity to 

another airport being visited by GAO, and size of airport. The results from

our airport visits provided examples of checked baggage screening 

operations and issues but cannot be generalized beyond the airports 

visited because we did not use statistical sampling in selecting the 

airports. We also conducted structured interviews with FSDs and their 

staffs who were responsible for 29 randomly selected airports. One FSD 

we interviewed was responsible for two airports in our sample. We 

conducted all but one of these interviews over the telephone. Using 

information from PMIS, we selected airports that had reported using 

alternative screening procedures and airports that had not reported using 

alternative screening procedures between October 18, 2004, and December 

21, 2004.

1

 Although the interviews were conducted with FSDs and their 

staffs at random samples of airports, the samples are too small to 

generalize the interview results with a high degree of statistical confidence 

to all airports nationwide. The results from these interviews do provide 

information about checked baggage screening operations at the airports 

for which the FSDs and their staffs are responsible. 

We conducted our work from September 2004 through July 2006 in 

accordance with generally accepted government auditing standards. 

 1

TSA has determined that the exact number of airports we selected is sensitive security 

information. 

Page 39 GAO-06-869 Aviation Security
Appendix II: Comments from the Department of Homeland 

Security

Page 40 GAO-06-869 Aviation Security

Appendix II: Comments from the Department 

of Homeland Security 
Appendix II: Comments from the Department of Homeland 

Security

Page 41 GAO-06-869 Aviation Security
Appendix II: Comments from the Department of Homeland 

Security

Page 42 GAO-06-869 Aviation Security
Related GAO Products 

Page 43 GAO-06-869 Aviation Security

Appendix III: GAO Contact and Staff 

Acknowledgments 

GAO Contact Cathleen A. Berrick (202) 512-3404 

In addition to the contact named above, David Alexander, Leo Barbour, 

Chuck Bausell Jr., Amy Bernstein, Kevin Copping, Katherine Davis, 

Josh Diosomito, Christine Fossett, Richard Hung, Benjamin Jordan, 

Thomas Lombardi, Lisa Shibata, Maria Strudwick, and Alper Tunca made 

key contributions to this report. 

Acknowledgments 
Related GAO Products 

Page 44 GAO-06-869 Aviation Security

Related GAO Products 

Aviation Security: TSA Has Strengthened Efforts to Plan for the Optimal 

Deployment of Checked Baggage Screening Systems but Funding 

Uncertainties Remain GAO-06-875T, June 29, 2006 

Aviation Security: Enhancements Made in Passenger and Checked 

Baggage Screening, but Challenges Remain. GAO-06-371T. Washington,

D.C.: April 4, 2006. 

Aviation Security: Transportation Security Administration Has Made

Progress in Managing a Federal Security Workforce and Ensuring 

Security at U.S. Airports, but Challenges Remain. GAO-06-597T. 

Washington, D.C.: April 4, 2006. 

Aviation Security: Progress Made to Set Up Program Using PrivateSector Airport Screeners, but More Work Remains. GAO-06-166. 

Washington, D.C.: March 31, 2006. 

Aviation Security: Significant Management Challenges May Adversely 

Affect Implementation of the Transportation Security Administration’s 

Secure Flight Program. GAO-06-374T. Washington, D.C.: February 9, 2006. 

Aviation Security: Federal Air Marshal Service Could Benefit from 

Improved Planning and Controls. GAO-06-203. Washington, D.C.: 

November 28, 2005. 

Aviation Security: Federal Action Needed to Strengthen Domestic Air 

Cargo Security. GAO-06-76. Washington, D.C.: October 17, 2005. 

Transportation Security Administration: More Clarity on the Authority 

of Federal Security Directors Is Needed. GAO-05-935. Washington, D.C.: 

September 23, 2005. 

Aviation Security: Flight and Cabin Crew Member Security Training 

Strengthened, but Better Planning and Internal Controls Needed. 

GAO-05-781. Washington, D.C.: September 6, 2005. 

Aviation Security: Transportation Security Administration Did Not 

Fully Disclose Uses of Personal Information during Secure Flight 

Program Testing in Initial Privacy Notes, but Has Recently Taken Steps

to More Fully Inform the Public. GAO-05-864R. Washington, D.C.: July 22, 

2005. 
Related GAO Products 

Aviation Security: Better Planning Needed to Optimize Deployment of 

Checked Baggage Screening Systems. GAO-05-896T. Washington, D.C.: 

July 13, 2005.

Aviation Security: Screener Training and Performance Measurement 

Strengthened, but More Work Remains. GAO-05-457. Washington, D.C.: 

May 2, 2005.

Aviation Security: Secure Flight Development and Testing Under Way, 

but Risks Should Be Managed as System Is Further Developed. GAO-05-

356. Washington, D.C.: March 28, 2005. 

Aviation Security: Systematic Planning Needed to Optimize the 

Deployment of Checked Baggage Screening Systems. GAO-05-365. 

Washington, D.C.: March 15, 2005. 

Aviation Security: Measures for Testing the Effect of Using Commercial

Data for the Secure Flight Program. GAO-05-324. Washington, D.C.: 

February 23, 2005. 

Transportation Security: Systematic Planning Needed to Optimize 

Resources. GAO-05-357T. Washington, D.C.: February 15, 2005. 

Aviation Security: Preliminary Observations on TSA’s Progress to Allow 

Airports to Use Private Passenger and Baggage Screening Services. 

GAO-05-126. Washington, D.C.: November 19, 2004. 

General Aviation Security: Increased Federal Oversight Is Needed, but 

Continued Partnership with the Private Sector Is Critical to Long-Term 

Success. GAO-05-144. Washington, D.C.: November 10, 2004. 

Aviation Security: Further Steps Needed to Strengthen the Security of 

Commercial Airport Perimeters and Access Controls. GAO-04-728. 

Washington, D.C.: June 4, 2004. 

Transportation Security Administration: High-Level Attention Needed 

to Strengthen Acquisition Function. GAO-04-544. Washington, D.C.: May 

28, 2004. 

Aviation Security: Challenges in Using Biometric Technologies. 

GAO-04-785T. Washington, D.C.: May 19, 2004. 

Page 45 GAO-06-869 Aviation Security
Related GAO Products 

Nonproliferation: Further Improvements Needed in U.S. Efforts to 

Counter Threats from Man-Portable Air Defense Systems. GAO-04-519. 

Washington, D.C.: May 13, 2004. 

Aviation Security: Private Screening Contractors Have Little Flexibility 

to Implement Innovative Approaches. GAO-04-505T. Washington, D.C.: 

April 22, 2004. 

Aviation Security: Improvement Still Needed in Federal Aviation 

Security Efforts. GAO-04-592T. Washington, D.C.: March 30, 2004. 

Aviation Security: Challenges Delay Implementation of ComputerAssisted Passenger Prescreening System. GAO-04-504T. Washington, D.C.: 

March 17, 2004. 

Aviation Security: Factors Could Limit the Effectiveness of the 

Transportation Security Administration’s Efforts to Secure Aerial 

Advertising Operations. GAO-04-499R. Washington, D.C.: March 5, 2004. 

Aviation Security: Computer-Assisted Passenger Prescreening System 

Faces Significant Implementation Challenges. GAO-04-385. Washington, 

D.C.: February 13, 2004. 

Aviation Security: Challenges Exist in Stabilizing and Enhancing 

Passenger and Baggage Screening Operations. GAO-04-440T. Washington,

D.C.: February 12, 2004. 

The Department of Homeland Security Needs to Fully Adopt a 

Knowledge-based Approach to Its Counter-MANPADS Development 

Program. GAO-04-341R. Washington, D.C.: January 30, 2004. 

Aviation Security: Efforts to Measure Effectiveness and Strengthen 

Security Programs. GAO-04-285T. Washington, D.C.: November 20, 2003. 

Aviation Security: Federal Air Marshal Service Is Addressing Challenges 

of Its Expanded Mission and Workforce, but Additional Actions Needed. 

GAO-04-242. Washington, D.C.: November 19, 2003. 

Aviation Security: Efforts to Measure Effectiveness and Address 

Challenges. GAO-04-232T. Washington, D.C.: November 5, 2003. 

Page 46 GAO-06-869 Aviation Security
Related GAO Products 

Airport Passenger Screening: Preliminary Observations on Progress 

Made and Challenges Remaining. GAO-03-1173. Washington, D.C.: 

September 24, 2003. 

Aviation Security: Progress Since September 11, 2001, and the 

Challenges Ahead. GAO-03-1150T. Washington, D.C.: September 9, 2003. 

Transportation Security: Federal Action Needed to Enhance Security 

Efforts. GAO-03-1154T. Washington, D.C.: September 9, 2003. 

Transportation Security: Federal Action Needed to Help Address 

Security Challenges. GAO-03-843. Washington, D.C.: June 30, 2003. 

Federal Aviation Administration: Reauthorization Provides 

Opportunities to Address Key Agency Challenges. GAO-03-653T. 

Washington, D.C.: April 10, 2003. 

Transportation Security: Post-September 11th Initiatives and LongTerm Challenges. GAO-03-616T. Washington, D.C.: April 1, 2003. 

Airport Finance: Past Funding Levels May Not Be Sufficient to Cover 

Airports’ Planned Capital Development. GAO-03-497T. Washington, D.C.: 

February 25, 2003. 

Transportation Security Administration: Actions and Plans to Build a 

Results-Oriented Culture. GAO-03-190. Washington, D.C.: January 17,

2003. 

Aviation Safety: Undeclared Air Shipments of Dangerous Goods and 

DOT’s Enforcement Approach. GAO-03-22. Washington, D.C.: January 10,

2003. 

Aviation Security: Vulnerabilities and Potential Improvements for the 

Air Cargo System. GAO-03-344. Washington, D.C.: December 20, 2002. 

Aviation Security: Registered Traveler Program Policy and 

Implementation Issues. GAO-03-253. Washington, D.C.: November 22, 

2002. 

Airport Finance: Using Airport Grant Funds for Security Projects Has 

Affected Some Development Projects. GAO-03-27. Washington, D.C.: 

October 15, 2002. 

Page 47 GAO-06-869 Aviation Security
Related GAO Products 

Commercial Aviation: Financial Condition and Industry Responses 

Affect Competition. GAO-03-171T. Washington, D.C.: October 2, 2002. 

Aviation Security: Transportation Security Administration Faces 

Immediate and Long-Term Challenges. GAO-02-971T. Washington, D.C.: 

July 25, 2002.

Aviation Security: Information Concerning the Arming of Commercial

Pilots. GAO-02-822R. Washington, D.C.: June 28, 2002. 

Aviation Security: Vulnerabilities in, and Alternatives for, Preboard 

Screening Security Operations. GAO-01-1171T. Washington, D.C.: 

September 25, 2001. 

Aviation Security: Weaknesses in Airport Security and Options for 

Assigning Screening Responsibilities. GAO-01-1165T. Washington, D.C.: 

September 21, 2001. 

Homeland Security: A Framework for Addressing the Nation’s 

Efforts. GAO-01-1158T. Washington, D.C.: September 21, 2001. 

Aviation Security: Terrorist Acts Demonstrate Urgent Need to Improve 

Security at the Nation’s Airports. GAO-01-1162T. Washington, D.C.: 

September 20, 2001. 

Aviation Security: Terrorist Acts Illustrate Severe Weaknesses in 

Aviation Security. GAO-01-1166T. Washington, D.C.: September 20, 2001. 

Page 48 GAO-06-869 Aviation Security (440517) 
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