Report to the Chairman, Subcommittee 

on Homeland Security, Committee on 

Appropriations, House of 

Representatives 

United States Government Accountability Office

GAO

March 2005 AVIATION SECURITY

Systematic Planning 

Needed to Optimize 

the Deployment of 

Checked Baggage 

Screening Systems 

GAO-05-365 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

www.gao.gov/cgi-bin/getrpt?GAO-05-365.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Cathleen A. 

Berrick at (202) 512-3404 or 

berrickc@gao.gov. 

Highlights of GAO-05-365, a report to the 

Chairman, Subcommittee on Homeland 

Security, Committee on Appropriations, 

House of Representatives 

March 2005

AVIATION SECURITY

Systematic Planning Needed to Optimize 

the Deployment of Checked Baggage 

Screening Systems 

TSA has made substantial progress in installing EDS and ETD systems at the 

nation’s more than 400 airports to provide the capability to screen all 

checked baggage using explosive detection systems, as mandated by 

Congress. However, in initially deploying EDS and ETD equipment, TSA 

placed stand-alone ETD and the minivan-sized EDS machines—mainly in 

airport lobbies—that were not integrated in-line with airport baggage 

conveyor systems. TSA officials stated that the agency’s ability to initially 

install in-line systems was limited because of the high costs and the time 

required for airport modifications. These interim lobby solutions resulted in 

operational inefficiencies, including requiring a greater number of screeners, 

as compared with using EDS machines in-line with baggage conveyor 

systems. 

TSA and airport operators are taking actions to install in-line baggage 

screening systems to streamline airport and TSA operations, reduce 

screening costs, and enhance security. Eighty-six of the 130 airports we 

surveyed either have, are planning to have, or are considering installing full 

or partial in-line systems. However, resources have not been made available 

to fund these capital-intensive systems on a large-scale basis. Also, the 

overall costs of installing in-line baggage screening systems at each airport 

are unknown, the availability of future federal funding is uncertain, and 

perspectives differ regarding the appropriate role of the federal government, 

airport operators, and air carriers in funding these systems. 

Moreover, TSA has not conducted a systematic, prospective analysis to 

determine at which airports it could achieve long-term savings and enhance 

efficiencies and security by installing in-line systems or, where in-line 

systems may not be economically justified, by making greater use of standalone EDS systems rather than relying on the labor-intensive and less 

efficient ETD screening process. However, at nine airports where TSA has 

agreed to help fund the installation of in-line baggage screening systems, 

TSA conducted a retrospective cost-benefit analysis which showed that 

these in-line systems could yield significant savings for the federal 

government. TSA further estimated that it could recover its initial 

investment in the in-line systems at these airports in a little over 1 year. 

EDS and ETD Machines Used by TSA to Screen Checked Baggage 

Mandated to screen all checked 

baggage using explosive detection 

systems at airports by December 

31, 2003, the Transportation 

Security Administration (TSA) 

deployed two types of screening 

equipment: explosives detection 

systems (EDS), which use 

computer-aided tomography X-rays 

to recognize the characteristics of 

explosives, and explosives trace 

detection (ETD) systems, which 

use chemical analysis to detect 

traces of explosive material vapors 

or residues. This report assesses 

(1) TSA’s use of budgeted funds to 

install EDS and ETD systems and 

the impact of initially deploying 

these systems, (2) TSA and airport 

actions to install EDS machines inline with baggage conveyor 

systems, and the federal resources 

made available for this purpose, 

and (3) actions taken by TSA to 

optimally deploy checked baggage 

screening systems. 

What GAO Recommends

GAO recommends that the 

Department of Homeland Security 

(DHS) direct TSA to take several 

actions needed to systematically 

evaluate baggage screening needs 

at airports, including identifying 

the costs and benefits of installing 

in-line EDS systems or stand-alone 

EDS machines in lieu of ETD 

machines, and prioritizing those 

airports where TSA would benefit 

by such actions. DHS generally 

concurred with GAO’s findings and 

recommendations and described 

corrective actions that it has 

initiated or plans to take to address 

the issues identified. 
Page i GAO-05-365 Aviation Security 

Letter 1

Results in Brief 3 

Background 6 

TSA Equipped More than 400 Airports to Screen Checked Baggage 

for Explosives, but the Initial Deployment Led to Operational 

Inefficiencies, and Additional Security Risks 13 

Airports and the Federal Government Are Taking Actions to Install 

In-line Baggage Screening Systems, but Resources Have Not 

Been Made Available to Fund These Systems on a Large-Scale 

Basis 26 

TSA Has Not Systematically Planned for the Optimal Deployment 

of Checked Baggage Screening Equipment to Ensure the 

Efficient and Cost-Effective Screening for Explosives while 

Enhancing Security Benefits 37 

Conclusions 45 

Recommendations for Executive Action 46 

Agency Comments and Our Evaluation 47 

Appendix I Objectives, Scope, and Methodology 50 

Appendix II Summary of Checked Baggage Screening 

Legislation 55 

Appendix III Airports Receiving TSA Airport Modification and 

EDS/ETD Equipment Installation Funding for In-line 

Systems 59 

Appendix IV Analysis of TSA’s Cost Savings Estimates for In-line 

EDS Checked Baggage Screening Systems 61 

Appendix V Comments from the Department of Homeland 

Security 66 

Contents 
Page ii GAO-05-365 Aviation Security 

Appendix VI GAO Contacts and Staff Acknowledgments 69 

GAO Contacts 69 

Staff Acknowledgments 69 

Glossary 70 

Tables 

Table 1: Airport Modification, Procurement, and Installation 

Funding for EDS/ETD Equipment for Fiscal Years 2002-

2004 15 

Table 2: Fiscal Year 2002-2004 Airport Modification and EDS/ETD 

Installation Obligations as of September 30, 2004 17 

Table 3: Fiscal Year 2002-2004 EDS/ETD Procurement Obligations 

as of September 30, 2004 19 

Table 4: EDS and ETD Machines Deployed at U.S. Airports as of 

June 2004 20 

Table 5: Average Percentage of Checked Baggage Reported as 

Screened Using EDS, ETD, or Other Approved Method at 

263 Airports on or around February 29, 2004 22 

Table 6: Bags Per Hour Screened by Stand-alone and In-line EDS 

Machines and ETD Machines 23 

Table 7: Source of Federal Funding Used for Airport Modification 

Planning and Construction of In-line EDS Systems as of 

July 2004 31 

Table 8: Airports Awarded LOIs 32 

Table 9: Highlights of Authorizations in Laws Related to Checked 

Baggage Screening in Aviation Transportation Security 

since the Terrorist Attacks of September 11, 2001 55 

Table 10: Highlights of Appropriations in Laws Related to Checked 

Baggage Screening in Aviation Transportation Security 

since the Terrorist Attacks of September 11, 2001 57 

Table 11: Listing of Airports Receiving Modification and EDS/ETD 

Equipment Installation Funding for Developing In-line EDS 

Baggage Screening Systems as of September 30, 2004 59 

Figures 

Figure 1: EDS Machine Used by TSA to Screen Checked Baggage 8 

Figure 2: ETD Machine Used by TSA to Screen Checked Baggage 8 
Page iii GAO-05-365 Aviation Security 

Figure 3: In-line Checked Baggage Screening System 11 

Figure 4: Crowded Airport Lobby with Stand-alone EDS Screening 26 

Figure 5: Status of In-line EDS Systems for Category X, I, and II 

Airports Included in Survey of Federal Security Directors 

as of July 2004 28 

Figure 6: TSA Criteria for Prioritizing Letters of Intent 38 

Figure 7: Airport Modification Costs Per In-line EDS Machine at 

Nine Airports 63 

Figure 8: Cost Savings from In-line EDS Systems Compared to 

Stand-alone EDS at Nine Airports 64 

Figure 9: Costs and Savings at Nine Airports 65 

Abbreviations 

ATSA Aviation and Transportation Security Act 

DHS Department of Homeland Security 

EDS explosives detection system 

ETD explosives trace detection 

FAA Federal Aviation Administration 

LOI letter of intent 

OMB Office of Management and Budget 

TSA Transportation Security Administration 

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 1 GAO-05-365 Aviation Security 

March 15, 2005 

The Honorable Harold Rogers 

Chairman 

Subcommittee on Homeland Security 

Committee on Appropriations 

House of Representatives 

Dear Mr. Chairman: 

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

Scotland, U.S. commercial aircraft have long been a target for terrorist 

attacks through the use of explosives carried in checked baggage. In 1996, 

the Federal Aviation Administration (FAA) established a long-term goal of 

screening all checked baggage for explosives to prevent such attacks and a 

timetable for deploying explosive detection systems at all airports by 2014. 

The terrorist attacks of September 11, 2001, however, increased the 

federal government’s focus on screening checked baggage for explosives 

at U.S. airports. On November 19, 2001, the Aviation and Transportation 

Security Act (ATSA)1

 was signed into law, creating the Transportation 

Security Administration (TSA) and mandating, among other things, the 

screening of all checked baggage 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) explosives detection systems (EDS), which use computeraided tomography X-rays adapted from the medical field to automatically 

recognize the characteristic signatures of threat explosives and 

(2) explosives trace detection (ETD), which uses chemical analysis to 

detect traces of explosive materials’ vapors and residue. 

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 the 2002 

congressionally established deadline to screen all checked baggage for 

explosives using EDS and ETD machines.2

 Recognizing the obstacles 

 1

Aviation and Transportation Security Act, Pub. L. No. 107-71, 115 Stat. 597 (2001). 

2

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

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

United States Government Accountability Office

Washington, DC 20548 
Page 2 GAO-05-365 Aviation Security 

encountered by TSA, Congress passed, and the President signed into law, 

the Homeland Security Act of 2002,3

 which, in effect, 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 

deploying and leveraging screening equipment and technologies. To 

further assess TSA’s efforts to deploy equipment and screen checked 

baggage for explosives using EDS and ETD, we addressed the following 

questions: (1) How did TSA use the funds it initially budgeted to procure 

and install EDS and ETD systems and make associated airport 

modifications, and what was the impact of the initial deployment of EDS 

and ETD systems? (2) What actions are airports and TSA currently taking 

to install automated in-line EDS baggage screening systems,4

 and what are 

the federal resources that have been made available to fund these 

systems? (3) What actions, if any, is TSA taking to plan for the optimal 

deployment of EDS and ETD equipment, including in-line checked 

baggage screening systems, in order to ensure the efficiency, cost 

effectiveness, and security of its checked baggage screening operations? 

To address these objectives, we reviewed available documentation on 

TSA’s checked baggage screening program, including contract obligations 

for modifying airports and procuring and installing EDS and ETD systems, 

inventory listings of EDS and ETD systems, funding and planning 

documentation for in-line systems, and cost analysis of in-line and standalone EDS equipment. Although we could not independently verify the 

reliability of all of this information, we compared it with other supporting 

documents, when available, to determine data consistency and 

reasonableness. On the basis of these efforts, we believe the information 

we obtained is sufficiently reliable for this report. We also reviewed the 

results of covert testing (undercover and unannounced) of checked 

baggage screening operations conducted by TSA’s Office of Internal 

Affairs and Program Review and questioned TSA officials about the 

procedures used to ensure the reliability of the covert test data. Based on 

their answers, we believe that the covert test data are sufficiently reliable 

for the purposes of our review. Further, we interviewed officials from 

 3

Homeland Security Act of 2002, Pub. L. No. 107-296, 116 Stat. 2135. 

4

In-line EDS checked baggage screening systems typically involve checked baggage 

undergoing automated screening with EDS machines while on a conveyor belt that sorts 

and transports baggage to the proper location for its ultimate loading onto an aircraft. 
Page 3 GAO-05-365 Aviation Security 

TSA, air carriers, airports, EDS and ETD equipment manufacturers, and 

airport industry associations to obtain information regarding TSA’s efforts 

to improve checked baggage screening operations using EDS machines. 

We performed our work at TSA headquarters and 22 airports throughout 

the United States. At the airports we visited, we observed baggage 

screening procedures and discussed these procedures with TSA, airport, 

and airline officials. We chose these 22 airports based on one or more of 

the following factors: a large number of passenger boardings, the 

existence of an operational in-line system, whether the airport had 

received or requested TSA funding for an in-line system, whether the 

airport had begun screening all checked baggage using EDS or ETD, and 

the proximity to a larger airport also being visited by GAO. In addition, we 

surveyed all 155 federal security directors, who oversee federal security 

operations at one or more airports in the United States where screening is 

required to obtain their perspectives on the implementation of checked 

baggage screening operations at 263 airports under their supervision, and 

to obtain information on these airports’ plans regarding the incorporation 

of EDS machines within the airports’ baggage conveyor systems for 

screening checked baggage for explosives. We conducted our work from 

September 2003 through January 2005 in accordance with generally 

accepted government auditing standards. A detailed discussion of our 

scope and methodology is contained in appendix I. Terms used in this 

report are further defined in a glossary at the end of this report. 

From its creation in November 2001 through September 2004, TSA 

obligated about $2.5 billion (93 percent) of the approximately $2.7 billion it 

had budgeted for fiscal years 2002 through 2004 for procuring and 

installing explosive detection equipment—predominantly to screen 

checked baggage for explosives—and making associated airport 

modifications to accommodate the equipment.5

 Specifically, TSA procured 

and placed about 1,200 EDS machines and about 6,000 ETD machines at 

over 400 airports and modified airports for the installation of this 

equipment. Although TSA made significant progress in fielding EDS and 

ETD equipment to the nation’s airports, TSA placed this equipment in a 

stand-alone mode—usually in airport lobbies—to conduct the primary 

screening of checked baggage for explosives, rather than integrating EDS 

machines in-line with airports’ baggage conveyor systems. TSA officials 

 5

Obligations are amounts of orders placed or contracts awarded during a given period that 

will require payment during the same or a future period. 

Results in Brief 
Page 4 GAO-05-365 Aviation Security 

stated that they use EDS machines in stand-alone mode and ETD 

machines as an interim solution in order to meet the congressional 

deadline for screening all checked baggage for explosives. Officials stated 

that they employed these interim solutions because of the significant costs 

required to install in-line systems and the need to reconfigure many 

airports’ baggage conveyor systems to accommodate the equipment. These 

interim screening solutions led to operational inefficiencies, including 

requiring a greater number of screeners and screening fewer bags for 

explosives each hour, as compared with using EDS machines in-line with 

baggage conveyor systems. Performing primary screening using ETD 

machines, as is the case for more than 300 airports, is more labor intensive 

and less efficient than screening using the EDS process. TSA’s placement 

of stand-alone EDS and ETD machines in airport lobbies also resulted in 

passenger crowding, which presented unsafe conditions and may have 

added security risks for passengers and airport workers. Certain 

information we obtained and analyzed regarding explosive detection 

technologies and their effectiveness in TSA’s checked baggage screening 

operations are classified or are considered by TSA to be sensitive security 

information. Accordingly, the results of our review of this information 

have been removed from this report.6

TSA and airport operators are taking actions to install in-line EDS baggage 

screening systems—to streamline airport and TSA operations, reduce 

screening costs, and enhance security—but resources have not been made 

available to fund these systems on a large-scale basis. Most airports that 

have installed or are planning to install these capital-intensive in-line 

systems have relied on or plan to rely on some form of federal funding to 

help install the systems. Although TSA and airports operators are taking 

actions to install in-line EDS baggage screening systems, identifying the 

resources to fund the systems on a large-scale basis continues to be a 

challenge. The issuance of letter of intent (LOI) agreements—TSA’s 

primary method for funding in-line systems—has been limited to nine 

airports. An LOI, though not a binding commitment of federal funding, 

represents an intent by TSA to provide funds in future years if they are 

 6

We issued two additional reports detailing the results of our review, which discuss results 

deemed to be classified or sensitive security information. The report that contains 

classified and sensitive security information is GAO, Aviation Security: Systematic 

Planning Needed to Optimize the Deployment of Checked Baggage Screening Systems, 

GAO-05-135C (Washington D.C.: February 4, 2005). The report containing sensitive security

information but not the classified information is GAO, Aviation Security: Systematic 

Planning Needed to Optimize the Deployment of Checked Baggage Screening Systems, 

GAO-05-302SU (Washington D.C.: February 4, 2005). 
Page 5 GAO-05-365 Aviation Security 

appropriated by Congress. This in turn enables an airport to proceed with 

a project, such as installing in-line baggage screening systems, because the 

airport and investors are aware that allowable costs will likely be 

reimbursed. Further, TSA has not determined the total cost of installing inline EDS baggage screening systems at airports determined to need these 

systems, the availability of funding for in-line systems is uncertain, and 

perspectives differ regarding the appropriate role of the federal 

government and airport operators in funding these systems. 

Moreover, TSA has not yet conducted the systematic analyses needed to 

plan for optimally deploying EDS and ETD equipment—including 

installing in-line EDS baggage screening systems or replacing ETD 

machines with stand-alone EDS machines—at the nation’s more than 

400 airports to enhance security and reduce TSA staffing requirements and 

long-term costs. Although TSA established criteria to prioritize airport 

eligibility for receiving LOI funds for in-line EDS systems and conducted a 

limited retrospective analysis for the nine airports that received LOI 

agreements, TSA has not conducted a prospective analysis to determine at 

which airports it could achieve long-term savings and improved security 

benefits by installing in-line baggage screening systems rather than 

continuing to rely on labor-intensive stand-alone EDS and ETD machines 

to screen checked baggage for explosives. TSA’s retrospective cost-benefit 

analysis conducted on the nine airports with signed LOI agreements to 

install in-line screening systems found that significant savings and other 

benefits, including reduced screener staffing requirements and increased 

baggage throughput, may be achieved through the installation of in-line 

systems. Also, for airports where in-line systems may not be economically 

justified because of the high cost of installing these systems, TSA has not 

conducted an analysis to determine whether it could achieve savings and 

other benefits by making greater use of stand-alone EDS systems rather 

than relying on the use of less efficient and more labor-intensive ETD 

machines at these airports. Further, although Congress has directed TSA 

to continue submitting quarterly reports on its plans for installing in-line 

baggage screening systems, TSA has not yet provided all of the 

information requested by Congress.7

 7

Conference Report 108-774 (Oct. 9, 2004), which accompanies the fiscal year 2005 

Department of Homeland Security Appropriations Act, Pub. L. No. 108-334, 118 Stat. 1298 

(2004), directs that TSA continue submitting quarterly reports on its plans for installing inline systems, consistent with similar language included in House Report 108-169 (June 23, 

2003), directing that TSA submit quarterly reports beginning September 1, 2003. 
Page 6 GAO-05-365 Aviation Security 

We are recommending that the Secretary of the Department of Homeland 

Security (DHS) direct the TSA Administrator to systematically evaluate 

baggage screening systems at the nation’s airports to include the costs and 

benefits associated with installing in-line EDS baggage screening systems 

and deploying stand-alone EDS machines—in lieu of ETD machines—to 

conduct the primary screening of checked baggage at airports where an inline system would not be cost-effective or for justified other reasons. We 

also made a recommendation to DHS addressing TSA’s protocols for 

screening checked baggage and associated screener training, which is 

included in the restricted versions of this report. 

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

comments, generally concurred with our findings and recommendations, 

and agreed that efforts to implement the recommendations are critical to a 

successful checked baggage screening program. DHS described some 

actions TSA has initiated to implement these recommendations, including 

conducting an analysis of the deployment of in-line checked baggage 

screening systems, and an analysis of those airports that would benefit 

from replacing ETDs with stand-alone EDS equipment. A copy of DHS’s 

comments is included as appendix V. 

With the passage of ATSA in November 2001, TSA assumed from FAA the 

majority of the responsibility for securing the commercial aviation 

system.8

 Under ATSA, TSA is responsible for ensuring that all baggage is 

properly screened for explosives at airports in the United States where 

screening is required, and for the procurement, installation, and 

maintenance of explosive detection systems used to screen checked 

baggage for explosives. ATSA required that TSA screen 100 percent of 

checked baggage using explosive detection systems by December 31, 2002. 

As it became apparent that certain airports would not meet the December 

2002 deadline to screen 100 percent of checked baggage for explosives, 

the Homeland Security Act of 2002 in effect extended the deadline to 

December 31, 2003, for noncompliant airports.9

 Prior to the passage of 

 8

For additional details on ATSA and other legislation related to checked baggage screening, 

see appendix II. 

9

ATSA also authorized the use of alternative means to screen checked baggage, such as 

positive passenger bag match (i.e., air carriers determining whether the passenger is on the 

same aircraft as the checked baggage), canine searches, and searches of bags by hand for 

time periods when airports were not able to screen 100 percent of checked baggage using 

explosive detection equipment. 

Background 
Page 7 GAO-05-365 Aviation Security 

ATSA in November 2001, only limited screening of checked baggage for 

explosives occurred. When this screening took place, air carriers had 

operational responsibility for conducting the screening, while FAA 

maintained oversight responsibility. With the passage of ATSA, TSA 

assumed operational responsibility from air carriers for screening checked 

baggage for explosives. Airport operators and air carriers continued to be 

responsible for processing and transporting passenger checked baggage 

from the check-in counter to the airplane. 

Explosive detection systems include EDS and ETD machines (see figs. 1 

and 2). EDS machines use computer-aided tomography X-rays adapted 

from the medical field to automatically recognize the characteristic 

signatures of threat explosives. 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 characteristic signatures of 

threat explosives. TSA has certified, procured, and deployed EDS 

machines manufactured by two companies. ETD machines work by 

detecting vapors and residues of explosives. Human operators collect 

samples by rubbing bags with swabs, which are chemically analyzed to 

identify any traces of explosive materials. ETD is used both for primary, or 

the initial, screening of checked baggage, as well as secondary screening, 

which resolves alarms from EDS machines that indicate the possible 

presence of explosives inside a bag. TSA has certified, procured, and 

deployed ETD machines from three manufacturers. 
Page 8 GAO-05-365 Aviation Security 

Figure 1: EDS Machine Used by TSA to Screen Checked Baggage 

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

The operational processes for conducting screening of checked baggage 

for explosives using ETD and EDS machines differ. Specifically, the ETD 

Source: GAO.
Page 9 GAO-05-365 Aviation Security 

screening process requires the screener to manually screen checked 

baggage by (1) swabbing an area of, or item in, the checked bag and 

(2) placing the swab in the ETD machine. The ETD machine then 

evaluates the sample on the swab to detect trace amounts of explosive 

residue. If these steps are not conducted correctly, the test may fail to 

detect explosives that are present. Since the first steps of this process 

require screeners to collect explosive particles, they are vulnerable to 

human error. In contrast, when using EDS machines as the primary means 

of detection, the screening is automated and the machine either alarms 

indicating the possible presence of explosives or does not alarm without 

screener involvement. 

As we reported in February 2004, to initially deploy EDS and ETD 

equipment to screen 100 percent of checked baggage for explosives, TSA 

implemented interim airport lobby solutions and in-line EDS baggage 

screening systems.10 The interim lobby solutions involved placing standalone EDS and ETD machines in the nation’s airports, most often in 

airport lobbies or baggage makeup areas where baggage is sorted for 

loading onto aircraft. For EDS in a stand-alone mode (not integrated with 

airport’s or air carrier’s baggage conveyor system) and ETD, TSA 

screeners are responsible for obtaining the passengers’ checked baggage 

from either the passenger or the air carrier, lifting the bags onto and off of 

EDS machines or ETD tables, using TSA protocols to appropriately screen 

the bags, and returning the cleared bags to the air carriers to be loaded 

onto departing aircraft. 

In addition to installing stand-alone EDS and ETD machines in airport 

lobbies and baggage makeup areas, TSA collaborated with some airport 

operators and air carriers to install integrated in-line EDS baggage 

screening systems within their baggage conveyor systems. While each inline baggage screening system is unique, these systems generally operate 

in a similar manner, as shown in figure 3. Typically, in-line systems involve 

checked baggage undergoing automated screening while on a conveyor 

belt that sorts and transports baggage to the proper location for its 

ultimate loading onto an aircraft. During this automated process, all 

checked baggage on the conveyor belt passes through EDS machines 

where the bags are screened for explosives. If no explosives are detected 

during this primary screening, the bag continues forward on the main 

conveyor belt to be loaded onto the aircraft. If an EDS machine alarms, 

 10GAO-04-440T.
Page 10 GAO-05-365 Aviation Security 

indicating the possibility of explosives, TSA screeners, by reviewing 

computer-generated images of the inside of the bag, attempt to determine 

whether a suspect item is actually a threat.11 If the screener determines 

that the suspect item is not a threat, the cleared bag continues on the 

conveyor belt system to be loaded onto the aircraft. If the screener is 

unable to make this determination, the bag is diverted from the main 

conveyor belt into an area where it receives a secondary screening in 

which the bag is opened and the contents of the bag are screened by a 

screener using an ETD machine and physical inspection. If the bag 

successfully clears secondary screening, it is placed on the main conveyor 

belt system to be loaded onto the aircraft. If the bag tests positive for 

explosives during secondary screening, TSA screeners are required to 

notify the appropriate officials. 

 11This review procedure is known as on-screen alarm resolution, which TSA began to 

implement in May 2004 after pilot testing the procedure at several airports. To enhance the 

efficiency of an in-line screening system, TSA also may network several EDS machines 

together so that images from multiple EDS machines that alarm can be sent to a centralized 

location for screeners to review and resolve using the on-screen resolution procedure. This 

process is known as “multiplexing.” 
Page 11 GAO-05-365 Aviation Security 

Figure 3: In-line Checked Baggage Screening System 

Both airports and the federal government have cooperated to jointly fund 

the installation of in-line EDS baggage screening systems. The federal 

government has used three funding mechanisms to modify airport 

Baggage loaded

onto airplane

CHECK-IN

Conveyor belt

leading to airplane

Conveyor belt

leading from check-in

to in-line system

Conveyor belt

leading to airplane

Conveyor belt leading

to secondary system

If EDS alarms, baggage

is sent to secondary screening

Complexity of conveyor

system will vary depending on

airport needs and configuration

EDS system for primary screening 

ETD machine

for secondary screening

Secondary

screening

area

Baggage

to check-in

Step 2a

Step 1a

Step 1b

Step 2b

If baggage passes

secondary screening it

is loaded onto airplane

If baggage tests 

positive for explosives 

during secondary 

screening, TSA 

screeners are 

required to notify 

appropriate officials.

When an EDS machine alarms, 

indicating the possibility of 

explosives, TSA 

screeners, by 

reviewing computergenerated images 

of the inside of the 

bag, attempt to 

determine whether 

or not suspect 

item(s) are in fact 

explosive materials.

Source: GAO and Nova Development Corporation.
Page 12 GAO-05-365 Aviation Security 

facilities to install in-line EDS systems—LOIs, other transaction 

agreements, and Airport Improvement Program funds from the FAA.12 In 

2003, Congress authorized TSA to issue LOIs for airport modifications 

related to the installation of in-line baggage screening systems.13 When an 

LOI is established to provide multiyear funding for a project, the airport 

operator is responsible for providing—up front—the total funding needed 

to complete the project, even though the LOI is not a binding commitment 

of federal funds. Work proceeds with the understanding that TSA will, if 

sufficient funding is appropriated, reimburse the airport operator for a 

percentage of the facility modification costs. Congress initially mandated a 

75 percent federal government cost-share for LOIs in February 2003, but in 

December of that year it increased the cost-share to 90 percent.14 However, 

the fiscal year 2005 DHS Appropriations Act subsequently re-established 

the federal government cost-share at 75 percent for fiscal year 2005. Also, 

the President’s fiscal year 2006 budget request for TSA proposes to 

maintain the 75 percent federal government cost share for projects funded 

by LOIs at large and medium airports. 

TSA also uses other transaction agreements, which are administrative 

vehicles used by TSA to directly fund airport operators engaged, or 

planning to engage, in smaller in-line airport modification projects without 

undertaking a long-term commitment. These transactions, which can take 

many forms and are generally not required to comply with federal laws 

and regulations that apply to contracts, grants, or cooperative agreements, 

enable the federal government and others entering into these agreements 

to freely negotiate provisions that are mutually agreeable. 

 12As described below and in appendix II, Congress has supported in-line EDS baggage 

screening systems by authorizing funding mechanisms and appropriating funds, and issuing 

calls for expediting the installation of such systems. However, Congress does not require 

that in-line systems be installed to satisfy the 100 percent explosive detection system 

screening mandate. 

13Consolidated Appropriations Resolution, 2003, Pub. L. No. 108-7, § 367, 117 Stat. 11. 

14The Consolidated Appropriations Resolution mandated that each LOI provide for a 

75 percent federal cost-share of the project’s cost, with the remaining 25 percent to be paid 

by the airport operator at airports with at least 0.25 percent of the total number of 

passenger boardings each year at all airports (and 90 percent for projects at all other 

airports). 

The Vision 100—Century of Aviation Reauthorization Act (Vision 100), Pub. L. No. 108-176, 

117 Stat. 2490 (2003), instituted a 90 percent federal cost-share of the project’s cost, with 

the remaining 10 percent to be paid by the airport operator at medium and large hub 

airports (and 95 percent for projects at any other airport). 
Page 13 GAO-05-365 Aviation Security 

In addition, airports have utilized Airport Improvement Program grants, 

which are awarded by the Secretary of Transportation for airport planning 

and development to maintain a safe and efficient nationwide system of 

public airports and for limited aviation security purposes. Some airport 

operators used the Airport Improvement Program in fiscal years 2002 and 

2003 to fund facility modifications needed to accommodate installing inline systems. However, provisions of ATSA and the Vision 100—Century of 

Aviation Reauthorization Act (Vision 100), as well as fiscal years 2004 and 

2005 appropriations language, have limited the future availability of the 

Airport Improvement Program to fund in-line systems.15

Since its inception in November 2001 through September 2004, TSA 

obligated about $2.5 billion (93 percent) of the approximately $2.7 billion it 

budgeted for fiscal years 2002 through 2004 for the procurement and 

installation of EDS and ETD machines to screen checked baggage for 

explosives and to modify airport facilities to accommodate this equipment. 

Although TSA made significant progress in fielding this equipment, TSA 

used most of the $2.5 billion to design, develop, and deploy interim lobby 

screening solutions rather than install more permanent in-line EDS 

baggage screening systems. TSA employed these as interim solutions in 

order to meet the congressional deadline for screening all checked 

baggage for explosives because of the significant costs required to install 

in-line systems and the need to reconfigure many airports’ baggage 

conveyor systems to accommodate the equipment. TSA officials also 

stated that they did not have time to conduct the planning needed or make 

airport modifications required for longer-term and more streamlined 

baggage screening operations. However, these interim lobby screening 

solutions used by TSA resulted in operational inefficiencies and additional 

security risks. Specifically, TSA’s use of stand-alone EDS and ETD 

machines required a greater number of screener staff and resulted in 

screening fewer bags for explosives per hour, as compared with using EDS 

 15Section 119 of ATSA significantly increased the amount of Airport Improvement Program 

funds available for security-related projects but also provided that this increase would be 

substantially reduced at the conclusion of fiscal year 2002. In December 2003, section 142 

of Vision 100 further reduced the availability of Airport Improvement Program funds by 

limiting the sources from which Airport Improvement Program funds could be used for 

security-related improvements. Subsequent prohibitions on the use of Airport Improvement 

Program funds for activities related to the installation of in-line explosive detection 

systems arose in the fiscal year 2004 Consolidated Appropriations Act, Pub. L. No. 108-199, 

118 Stat. 283, enacted in January 2004, and again in the fiscal year 2005 Consolidated 

Appropriations Act, Pub. L. No. 108-447, 118 Stat. 2809, enacted in December 2004. 

TSA Equipped More 

than 400 Airports to 

Screen Checked 

Baggage for 

Explosives, but the 

Initial Deployment 

Led to Operational 

Inefficiencies, and 

Additional Security 

Risks 
Page 14 GAO-05-365 Aviation Security 

machines in-line with baggage conveyor systems. Also, screening with 

ETD machines, as is the case for more than 300 airports, is more laborintensive and less efficient than screening using the EDS process. TSA 

officials also raised concerns about the possible security risks caused by 

baggage screening equipment being located in airport lobbies—causing 

overcrowding due to passengers waiting to have their bags screened. 

TSA used most of the airport modification and equipment procurement 

and installation funds to deploy interim lobby screening solutions at more 

than 400 airports to provide the means for screening all checked baggage 

for explosives as mandated by the Congress. As shown in table 1, the 

Congress earmarked about $1.5 billion of the $2.7 billion budgeted amount 

specifically to install EDS and ETD equipment, and to modify and prepare 

airport facilities to incorporate the use of this equipment for screening 

checked baggage for explosives. Congress earmarked and TSA budgeted 

the remaining $1.2 billion for the procurement of EDS and ETD machines. 

TSA Procured and 

Installed Explosive 

Detection Equipment and 

Modified Airports to 

Integrate this Equipment 

to Screen Checked 

Baggage for Explosives 
Page 15 GAO-05-365 Aviation Security 

Table 1: Airport Modification, Procurement, and Installation Funding for EDS/ETD Equipment for Fiscal Years 2002-2004 

Dollars in millions 

Public law

Airport modification 

and EDS/ETD 

installation funds

EDS/ETD 

procurement 

funds Total

Fiscal year 2002 TSA budget (not earmarked) 

EDS/ETD procurement $0.0 $703.5 $703.5

Other nonearmarked TSA funding $0.0 $156.0 $156.0

Total nonearmarked budget $0.0 $859.5 $859.5

Earmarked TSA appropriationsa 

Fiscal year 02 supplemental 107-206 $738.0 $738.0

Fiscal year 03 consolidation 108-7 $265.0 $174.5 $439.5

Fiscal year 03 emergency wartime supplemental 108-11 $235.0 $235.0

Fiscal year 04 DHS appropriations 108-90 $249.4 $149.7 $399.1

Total earmarked appropriations $1,487.4 $324.2 $1,811.6

Total fiscal year 2002-2004 EDS/ETD fundingb $1,487.4 $1,183.6 $2,671.1

Less amount obligated as of September 30, 2004 ($1,307.4) ($1,183.4) ($2,490.8)

Amount available for additional obligation as of 

September 30, 2004b

$180.0 $0.3 $180.3

Source: GAO analysis of TSA data. 

a

These earmarked appropriations are funds that Congress has specified can be spent by TSA only for 

the particular purpose indicated in the table. 

b

Totals may not add because of rounding. 

As of the end of fiscal year 2004, TSA used about one-half of the 

$2.5 billion that it had obligated to modify airport facilities and to install 

EDS and ETD machines, and the remaining half primarily to procure EDS 

and ETD machines. As of September 30, 2004, TSA had obligated 

approximately $1.3 billion of the approximately $1.5 billion that had been 

earmarked for airport modifications and the installation of EDS and ETD 

equipment. As shown in table 2, TSA had used about $885 million (about 

68 percent) of these obligated funds for the general deployment and 

installation of EDS and ETD equipment at various airports as part of 

interim lobby solutions to quickly install checked baggage screening 

equipment. Also included in this amount are funds that TSA used for 

installing interim partial in-line baggage screening systems at some 

airports. In general, these systems were for sections of an airport, were 

not fully integrated into the airport’s baggage handling system, and most 

often were temporary until a permanent in-line system could be installed. 

For example, TSA awarded the Port of Seattle about $9 million for the 

construction of interim partial in-line systems and modification of the 
Page 16 GAO-05-365 Aviation Security 

baggage handling systems serving four airlines at the Seattle-Tacoma 

International Airport. These interim partial in-line systems, which are not 

fully integrated with the baggage handling systems, will be replaced by 

permanent in-line baggage screening systems that will be fully integrated 

with the airport’s baggage handling systems by March 2007. Most of the 

remaining airport modification and equipment installation obligations are 

being used by TSA for work related to the permanent in-line integration of 

EDS baggage screening equipment into airportwide or individual terminal 

baggage conveyor systems at 33 airports. See appendix III for a listing of 

the 33 airports having in-line baggage screening systems installed and the 

source of TSA funding for the in-line systems. 
Page 17 GAO-05-365 Aviation Security 

Table 2: Fiscal Year 2002-2004 Airport Modification and EDS/ETD Installation Obligations as of September 30, 2004 

Dollars in millions 

Reason for obligation Amount obligated Percentageb

Funding for general interim lobby deployment and integration of EDS and ETD 

equipment for screening checked baggage 

 

Planning, designing, and airport structural modification work performed at over 400 airports 

by TSA’s prime contractor, Boeing Service Company and its subcontractorsa $843.3

Work performed by other individual contractors and EDS manufacturers $32.8

Costs associated with transporting and upgrading EDS/ETD equipment $8.5

Subtotalb $884.7 68

Funding for permanent in-line integration of EDS screening equipment into airportwide 

or individual terminal baggage conveyor systems at 33 airports 

Initial letter of intent funding to nine airports for airport modification $259.4

Other transaction agreement funding to eight airports for airport modification $82.6

Airport modification and EDS equipment installation work performed by Boeing Service 

Company, other contractors, and EDS manufacturers at 25 airports $52.2

Subtotalb$394.3 30

Funding for engineering, testing, and analytical support services 

Engineering, testing, and analytical support services to TSA for airport facility modification and 

EDS/ETD installation activities $28.4 2

Total obligatedb $1,307.4

Source: GAO analysis of TSA data. 

a

Some of these funds were used for the permanent in-line installation and integration of EDS 

equipment into baggage conveyor systems at eight airports including two category X, and six 

category I and II airports. We were unable to determine the amount expended for this effort because 

at the time the work was accomplished, TSA did not require Boeing Service Company, the prime 

contractor responsible for deploying EDS and ETD equipment, to track obligations and expenditures 

at the airport level. 

b

Totals and subtotals may not add because of rounding. 

TSA contracted with Boeing Service Company in June 2002 to be the 

prime contractor for deploying EDS and ETD equipment at the nation’s 

airports. This effort involved designing and implementing airport facility 

modifications for EDS and ETD equipment, such as new construction, 

infrastructure reinforcement, and modification of electrical systems 

required to install the EDS and ETD equipment. Originally, the period of 

performance for this contract was to expire on December 31, 2002. 

However, TSA extended the contract’s period of performance in order for 

Boeing to perform activities associated with installing interim lobby 

solutions to help airports meet or to maintain compliance to screen 

100 percent of checked baggage with explosive detection systems. These 

contract extensions have resulted in a $486.3 million increase in TSA 
Page 18 GAO-05-365 Aviation Security 

obligations against this contract for work related to airport modifications 

and EDS and ETD installation from $372.6 million in fiscal year 2002 to 

$858.8 million as of September 30, 2004.16 Boeing had expended most 

(98 percent) of these funds for interim lobby screening solutions. 

As of September 30, 2004, TSA had obligated almost 100 percent of the 

approximately $1.2 billion that had been budgeted or earmarked for 

procurement of EDS and ETD machines. As shown in table 3, about 

80 percent of these funds has been obligated for procuring EDS machines, 

with most of the remaining funding being obligated for procuring ETD 

machines. 

 16As of September 30, 2004, TSA has obligated $1.3 billion against the Boeing contract; in 

addition to the $858.8 million for airport modification and EDS/ETD installation, Boeing is 

receiving $297.4 million for EDS/ETD maintenance, $134.9 million for training baggage 

screeners, and $2.5 million for EDS/ETD transportation and other costs. 
Page 19 GAO-05-365 Aviation Security 

Table 3: Fiscal Year 2002-2004 EDS/ETD Procurement Obligations as of September 30, 2004 

Dollars in millions Amount obligated 

Item/task description 

Number of 

units Subtotal Total Percent

Procurement of EDS machines and associated equipment 

Invision EDS machines and associated equipment 

CTX 2500 EDS designed for stand-alone configuration 82 $31.0 

CTX 5500 EDS designed for both stand-alone or in-line 

configurations 357 $190.5 

 

CTX 9000 EDS designed for in-line configuration 246 $284.4 

EDS machine manufacturing ramp-up, engineering services and 

other costs $17.3 

 

L3 Examiner 6000 EDS designed for both stand-alone or in-line 

configurations 519 $428.7 

 

Total EDS procurement 1,204 $951.9 80

Procurement of ETD machines, parts and consumables 

Ionscan 400B ETD machines, parts, and consumables 3,162 $121.5 

Itemiser ETD machines, parts, and consumables 1,785 $65.5 

EGIS-II ETD machines, parts, and consumables 700 $32.5 

Total ETD procurement 5,647 $219.5 19

Other services and equipment procurement 

Other engineering, testing, and analytical support services to TSA 

for airport facility modification and EDS/ETD installation activities 

 

$6.6 

 

X-ray machines and other services $3.6 

Transportation of EDS equipment within and between airports $1.0 

Other charges for services and supplies $0.9 

Total other services and equipment $12.1 1

Total obligateda $1,183.4 

Source: GAO analysis of TSA data. 

a

Total does not add because of rounding. 

Table 4 summarizes the location of EDS and ETD equipment at the 

nation’s airports by airport category,17 based on a June 2004 TSA inventory 

listing. The number of machines shown in table 4 includes EDS and ETD 

 17 TSA 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 20 GAO-05-365 Aviation Security 

machines procured by both TSA and FAA prior to and during the 

establishment of TSA. 

Table 4: EDS and ETD Machines Deployed at U.S. Airports as of June 2004 

Number 

Airport category Airports EDS machines ETD machines

X 21 679 2,833

I 61 467 2,401

II 50 71 695

III 124 9 744

IV 190 2 473

Total 446 1,228 7,146

Source: GAO analysis of TSA data. 

Although TSA made significant progress in fielding EDS and ETD 

equipment to the nation’s airports to screen checked baggage for 

explosives, as mandated by Congress, TSA primarily used this equipment 

as part of interim lobby solutions to screen checked baggage for 

explosives, rather than the permanent integration of EDS machines in-line 

with airport baggage conveyor systems. TSA fielded most of the EDS and 

ETD machines needed to screen checked baggage for explosives to the 

nation’s over 400 airports by the congressionally mandated date of 

December 2003 (extended from the original deadline of December 2002), 

despite limited time to deploy the equipment and some of the equipment 

not being available when needed. In 1996, FAA, the organization then 

responsible for the procurement of checked baggage screening equipment, 

established a long-term goal of fielding explosive detection systems at all 

airports within 18 years—by 2014. As of June 2002, we reported that FAA 

had fielded 200 EDS and 200 ETD systems to 56 airports.18 In about two 

and one-half years following the mandate to screen all checked baggage 

for explosives, TSA’s deployment of equipment resulted in 1,228 EDS 

machines and 7,146 ETD machines being available in over 400 airports, as 

shown in table 4. Initially, EDS manufacturers were unable to produce and 

deliver the number of machines needed by TSA, and TSA determined that 

a mix of EDS and ETD technologies would provide an efficient and 

effective means of passenger protection. 

 18GAO, Aviation Security: Transportation Security Administration Faces Immediate 

and Long-Term Challenges, GAO-02-971T (Washington, D.C.: July 25, 2002).

TSA’s Initial Deployment of 

EDS and ETD Machines 

Resulted in Interim 

Solutions for Screening 

with Stand-alone 

Equipment Located Mainly 

in Airport Lobbies 
Page 21 GAO-05-365 Aviation Security 

During our site visits to 22 category X, I, and II airports, we observed that 

in most cases, TSA used stand-alone EDS machines and ETD machines as 

the primary method for screening checked baggage.19 Generally, this 

equipment was located in airport lobbies and in baggage makeup areas. In 

addition, in our survey of 155 federal security directors, we asked the 

directors to estimate, for the 263 airports included in the survey, the 

approximate percentage of checked baggage that was screened on or 

around February 29, 2004, using EDS, ETD, or other approved alternatives 

for screening baggage such as positive passenger bag match or canine 

searches.20 As shown in table 5, the directors reported that for 

130 large to medium-sized airports in our survey (21, 60, and 49 category X, 

I, and II airports, respectively), most of the checked baggage was screened 

using stand-alone EDS or ETD machines. The average percentage of 

checked baggage reported as screened using EDS machines at airports 

with partial or full in-line EDS capability ranged from 4 percent for 

category II airports to 11 percent for category X airports. In addition, the 

directors reported that ETD machines were used to screen checked 

baggage 93 to 99 percent of the time at category III and IV airports, 

respectively. 

 19The 22 airports included 12 category X, 9 category I, and 1 category II airports. 

20A TSA federal security director oversees federal security operations at one or more U.S. 

commercial airports and has operational responsibility for the screening of passengers and 

checked baggage. 
Page 22 GAO-05-365 Aviation Security 

Table 5: Average Percentage of Checked Baggage Reported as Screened Using 

EDS, ETD, or Other Approved Method at 263 Airports on or around February 29, 

2004 

Airport category X I II III IV Total

Number of airports 21 60 49 73 60 263

Percentage of checked baggage screened using: 

EDS (at airports with no in-line EDS 

capability) 59 59 27 6 0 25

EDS (at airports with partial or 

airportwide in-line EDS capability) 11 8 4 0 0 3

Totala EDS 70 67 32 6 0 28

ETD 18 33 66 93 99 69

Totala EDS and ETD 88 99 98 99 99 98

Other approved method 12 1 2 2 1 2

Totala 100 100 100 100 100 100

Source: Analysis of GAO federal security director survey data. 

a

Percentages may not add because of rounding. 

TSA’s interim solution of using stand-alone EDS and ETD machines as the 

primary method to screen checked baggage for explosives led to 

operational inefficiencies including (1) the increased use of screener staff, 

(2) a lower baggage throughput rate per hour for screening baggage for 

explosives, and (3) an increase in on-the-job injuries. Further, at many 

airports, TSA’s placement of the minivan-sized stand-alone EDS machines 

and ETD machines in airport lobbies at times resulted in passenger 

crowding, which presented unsafe conditions and may have added 

security risks for passengers and airport workers. 

Stand-alone EDS and ETD machines are both labor- and time-intensive to 

operate since each bag must be physically carried to an EDS or ETD 

machine for screening and then moved back to the baggage conveyor 

system prior to being loaded onto an aircraft. With an in-line EDS system, 

checked baggage is screened within an airport’s baggage conveyor system, 

eliminating the need for a baggage screener or other personnel to 

physically transport the baggage from the check-in point to the EDS 

machine for screening and then to the airport baggage conveyor system. 

Further, according to TSA officials, ETD machines and stand-alone EDS 

machines are less efficient in the number of checked bags that can be 

screened per hour per machine than are EDS machines that are integrated 

in-line with the airport baggage conveyor systems. As shown in table 6, as 

Interim Solutions Resulted 

in Operational 

Inefficiencies and 

Additional Security Risks 
Page 23 GAO-05-365 Aviation Security 

of October 2003, TSA estimated that the number of checked bags screened 

per hour could more than double when EDS machines were placed in-line 

versus being used in a stand-alone mode. According to a senior TSA 

official in the Office of Security Technology, these throughput numbers 

could change as TSA gains greater operational experience. 

Table 6: Bags Per Hour Screened by Stand-alone and In-line EDS Machines and 

ETD Machines 

Bags per hour 

Type of equipment Stand-alone In-line

EDS machines 

CTX 2500—stand-alone only 120 NA

CTX 5500 180 250

CTX 9000—in-line only NA 425

L3 6000 180 425

ETD machines—stand-alone only 36 NA

Source: TSA. 

NA: Not applicable. 

In January 2004, TSA, in support of its planning, budgeting, and acquisition 

of security screening equipment, reported to the Office of Management 

and Budget (OMB) that the efficiency benefits of in-line rather than standalone EDS are significant, particularly with regard to bags per hour 

screened and the number of TSA screeners required to operate the 

equipment. According to TSA officials, at that time, a typical lobby-based 

screening unit consisting of a stand-alone EDS machine with three ETD 

machines had a baggage throughput of 376 bags per hour with a staffing 

requirement of 19 screeners. In contrast, TSA estimated that 

approximately 425 bags per hour could be screened by in-line EDS 

machines with a staffing requirement of 4.25 screeners. 

In order to achieve the higher throughput rates and reduce the number of 

screener staff needed to operate in-line baggage screening systems, TSA 

(1) uses a screening procedure known as “on-screen alarm resolution” and 

(2) networks multiple in-line EDS machines together, referred to as 

“multiplexing,” so that the computer-generated images of bags from these 

machines are sent to a central location where TSA screeners can monitor 

the images of suspect bags centrally from several machines using the onscreen alarm resolution procedure. When an EDS machine alarms, 

indicating the possibility that explosive material may be contained in the 

bag, the on-screen alarm resolution procedure allows screeners to 
Page 24 GAO-05-365 Aviation Security 

examine computer-generated images of the inside of a bag to determine if 

suspect items identified by the EDS machines are in fact suspicious. If a 

screener, by viewing these images, is able to determine that the suspect 

item or items identified by the EDS machine are in fact harmless, the 

screener is allowed to clear the bag, and it is sent to the airline baggage 

makeup area for loading onto the aircraft. If the screener is not able to 

make the determination that the bag does not contain suspicious objects, 

the bag is sent to a secondary screening room where the bag is further 

examined by a screener. In secondary screening, the screener opens the 

bag and examines the suspect item or items, and usually swabs the items 

to collect a sample for analysis using an ETD machine. TSA also uses this 

on-screen alarm resolution procedure with stand-alone EDS machines.21

A TSA official estimated that the on-screen alarm resolution procedure 

with in-line EDS baggage screening systems will enable TSA to reduce by 

40 to 60 percent the number of bags requiring the more labor-intensive 

secondary screening using ETD machines. In estimating the potential 

savings in staffing requirements, TSA officials stated that they expect to 

achieve a 20 to 25 percent savings because of reductions in the number of 

staff needed to screen bags using ETD to resolve alarms from in-line EDS 

machines. 

TSA also reported that because procedures for using stand-alone EDS and 

ETD machines require screeners to lift heavy baggage onto and off of the 

machines, the interim lobby screening solutions used by TSA led to 

significant numbers of on-the-job injuries.22 In addition, in responding to 

our survey about 263 airports, numerous federal security directors 

reported that on-the-job injuries related to lifting heavy baggage onto or 

off the EDS and ETD machines were a significant concern at the airports 

for which they were responsible. Specifically, these federal security 

directors reported that on-the-job injuries caused by lifting heavy bags 

onto and off of EDS machines were a significant concern at 65 airports, 

and were a significant concern with the use of ETD machines at 

110 airports. To reduce on-the-job injuries, TSA has provided training to 

screeners on proper lifting procedures. However, according to TSA 

officials, in-line EDS screening systems would significantly reduce the 

 21TSA began implementing the on-screen alarm resolution procedure in May 2004 after pilot 

testing the procedure. 

22TSA was unable to provide GAO with data on the on-the-job injuries sustained during 

baggage screening operations. 
Page 25 GAO-05-365 Aviation Security 

need for screeners to handle baggage, thus further reducing the number of 

on-the-job injuries being experienced by TSA baggage screeners. 

In addition, during our site visits to 22 large and medium-sized airports, 

several TSA, airport, and airline officials expressed concern regarding the 

security risks caused by overcrowding due to ETD and stand-alone EDS 

machines being located in airport lobbies. The location of the equipment 

resulted in less space available to accommodate passenger movement and 

caused congestion due to passengers having to wait in lines in public areas 

to have their checked baggage screened. TSA headquarters officials also 

reported that large groups of people congregating in crowded airport 

lobbies, as shown in figure 4, increases security risks by creating a 

potential target for terrorists. The TSA officials noted that crowded airport 

lobbies have been the scenes of terrorist attacks in the past. For example, 

in December 1985, four terrorists walked to the El Al ticket counter at 

Rome’s Leonardo DaVinci Airport and opened fire with assault rifles and 

grenades, killing 13 and wounding 75. On that same day, three terrorists 

killed three people and wounded 30 others at Vienna International Airport. 
Page 26 GAO-05-365 Aviation Security 

Figure 4: Crowded Airport Lobby with Stand-alone EDS Screening 

Airport operators and TSA are taking actions to install in-line EDS baggage 

screening systems because of the expected benefits of these systems. 

However, airport operators and TSA have made limited progress in 

installing in-line baggage screening systems on a large-scale basis because 

sufficient resources have not been made available for the installation of 

these capital-intensive systems. To install in-line systems, airport 

operators and TSA work cooperatively, with airport operators responsible 

for the baggage conveyor systems and utilities, and TSA responsible for 

the EDS and ETD machines. Airport operators and TSA have also shared 

in the total costs—25 percent and 75 percent respectively under LOI 

agreements, which have been TSA’s primary method for funding in-line 

systems. Most airports that have installed or are planning to install in-line 

systems have relied on or plan to rely on some form of federal funding to 

help install the systems. However, as of January 2005, TSA has not used 

LOIs to fund the installation of in-line systems beyond nine airports. 

Further, TSA has not determined the total cost of installing in-line EDS 

baggage screening systems at airports determined to need these systems. 

In addition, perspectives differ regarding the appropriate role of the 

federal government and airport operators in funding these systems. 

Airports and the 

Federal Government 

Are Taking Actions to 

Install In-line Baggage 

Screening Systems, 

but Resources Have 

Not Been Made 

Available to Fund 

These Systems on a 

Large-Scale Basis 

Source: TSA.
Page 27 GAO-05-365 Aviation Security 

Airport operators and TSA are taking actions to install in-line EDS baggage 

screening systems because of the expected benefits of these systems. Our 

survey of federal security directors and interviews with airport officials 

revealed that 86 of 130 category X, I, and II airports (66 percent) included 

in our survey either have, are planning to have, or are considering 

installing in-line EDS baggage screening systems throughout or at a 

portion of their airports. As shown in figure 5, as of July 2004, 12 airports 

had operational in-line systems airportwide or at a particular terminal or 

terminals, and an additional 45 airports were actively planning or 

constructing in-line systems. Our survey of federal security directors 

further revealed that an additional 33 of the 130 category X, I, and II 

airports we surveyed were considering developing in-line systems. 

Many Airports Have, Are 

Planning to Have, or Are 

Considering Installing Inline EDS Baggage 

Screening Systems 
Page 28 GAO-05-365 Aviation Security 

Figure 5: Status of In-line EDS Systems for Category X, I, and II Airports Included in Survey of Federal Security Directors as of 

July 2004 

a

The total number of airports having, planning to have, or considering an in-line system is 86. The pie 

charts above include three category X and one category I airports twice because they currently have 

operating in-line systems either covering the total airport or a particular terminal or terminals and are 

in the process of planning and constructing additional in-line systems. 

In addition to the expected benefits of reduced TSA screening personnel, 

enhanced security, and increased baggage throughput, airport officials 

anticipate that they will be able to streamline their airport 
Page 29 GAO-05-365 Aviation Security 

operations from installing in-line baggage screening systems. For example, 

some airport and air carrier officials we interviewed anticipate that in-line 

systems will result in less congestion at airline ticket counters by 

removing stand-alone EDS and ETD machines from crowded airport 

lobbies, thereby improving airline passenger flow and queuing in the 

terminals by not forcing passengers to wait in long lines at ticket counters 

to have their bags screened. Officials also believe that the installation of 

in-line systems would allow for airport growth because in-line EDS 

systems could screen checked baggage faster than stand-alone EDS and 

ETD systems and could be upgraded to accommodate growth in airline 

passenger traffic. Officials further stated that in-line systems would allow 

them to retain greater control and autonomy of their baggage handling 

systems by creating a streamlined process for moving checked baggage 

directly from where baggage is checked to the aircraft. 

While in-line EDS baggage screening systems have a number of potential 

benefits, the total cost to install these systems is unknown, and limited 

federal resources have been made available to fund these systems on a 

large-scale basis. In-line baggage screening systems are capital-intensive 

because they often require significant airport modifications, including 

terminal reconfigurations, new conveyor belt systems, and electrical 

upgrades. 

TSA has not determined the total cost of installing in-line EDS baggage 

screening systems at airports that it had determined need these systems to 

maintain compliance with the congressional mandate to screen all 

checked baggage for explosives using explosive detection systems, or to 

achieve more efficient and streamlined checked baggage screening 

operations. However, TSA and airport industry association officials have 

estimated that the total cost of installing in-line systems is—a rough orderof-magnitude estimate—from $3 billion to more than $5 billion. TSA 

officials stated that they have not conducted a detailed analysis of the 

costs required to install in-line EDS systems at airports because most of 

their efforts have been focused on deploying and maintaining a sufficient 

number of EDS and ETD machines to screen all checked baggage for 

explosives. TSA officials further stated that the estimated costs to install 

in-line baggage screening systems would vary greatly from airport to 

airport depending on the size of the airport and the extent of airport 

modifications that would be required to install the system. While we did 

not independently verify the estimates, officials from the Airports Council 

International-North America and American Association of Airport 

Executives estimated that project costs for in-line systems could range 

Total Costs of In-line EDS 

Baggage Screening 

Systems Are Unknown, 

and Federal Resources 

Have Not Been Made 

Available to Fund These 

Systems on a Large-Scale 

Basis 
Page 30 GAO-05-365 Aviation Security 

from about $2 million for a category III airport to $250 million for a 

category X airport.23

Airport operators have relied on several sources of federal funding to help 

pay for the planning and construction of in-line EDS baggage screening 

systems. We interviewed airport officials from 53 airports that either have 

or are in the process of planning or constructing in-line systems to 

determine the extent to which they have relied on or plan to rely on 

federal funding to install in-line systems.24 As shown in table 7, officials at 

42 of the 53 airports we interviewed reported that they relied on the use of 

federal funds from the FAA Airport Improvement Program and TSA to 

help fund the planning and construction of these systems. However, there 

was no readily available information that would allow us to determine to 

what extent these 42 airports relied on or plan to rely on the use of federal 

funds for constructing or planning their in-line systems. Only one of the 53 

airports completed its in-line system without first receiving federal funds 

for the project, while an additional 10 airports have started planning or 

constructing their in-line systems without receiving federal assistance or a 

commitment to receive federal assistance. 

 23Joint Statement of David Z. Plavin, President, Airports Council International-North 

America (ACI-NA) and Todd Hauptli, Sr. Executive Vice President, American Association 

of Airport Executives (AAAE) before the House Aviation Subcommittee Hearing on 

Passenger and Baggage Screening Problems; February 12, 2004. GAO did not independently 

verify cost figures provided in this testimony. 

24These 53 airports were among 70 airports identified by federal security directors during 

our Web-based survey as either having or in the process of planning or constructing in-line 

systems. Officials at the remaining 17 airports indicated that their airports had not 

developed plans for in-line baggage screening systems. 
Page 31 GAO-05-365 Aviation Security 

Table 7: Source of Federal Funding Used for Airport Modification Planning and 

Construction of In-line EDS Systems as of July 2004 

Number by airport category 

X I II Total

Airports that have either constructed 

or are in the process of planning 19 27 7 53

Source of federal funding used 

Combination of Airport 

Improvement Program and TSA 

funding 5 0 0 5

Airport Improvement Program 

funding only 7 17 4 28

TSA funding only 3 5 1 9

Total 15 22 5 42

No federal funding used 4 5 2 11

Source: GAO analysis of information received from interviews with airport officials. 

TSA and airport operators are relying on LOI agreements as their principal 

method for funding the modification of airport facilities to incorporate inline baggage screening systems. The fiscal year 2003 Consolidated 

Appropriations Resolution approved the use of LOIs as a vehicle to 

leverage federal government and industry funding to support facility 

modification costs for installing in-line EDS baggage screening systems. 

When an LOI is established to provide multiyear funding for a project, the 

airport operator is responsible for providing—up front—the total funding 

needed to complete the project, even though the LOI is not a binding 

commitment of federal funds. Work proceeds with the understanding that 

TSA will, if sufficient funding is appropriated, reimburse the airport 

operator for a percentage of the facility modification costs, with the 

airport funding the remainder of the costs. LOIs issued by TSA for in-line 

baggage screening systems provide for reimbursement payments over a 

multiple year period, contingent upon the appropriation of sufficient 

funding to cover such projects. 

As of January 2005, TSA had issued eight LOIs to reimburse nine airports 

for the installation of in-line EDS baggage screening systems for a total 

cost of $957.1 million to the federal government over 4 years. In addition, 

TSA officials stated that as of July 2004, they had identified 

27 additional airports that they believe would benefit from receiving LOIs 

for in-line systems because such systems are needed to screen an 

increasing number of bags due to current or projected growth in passenger 

traffic. TSA officials stated that without such systems, these airports 
Page 32 GAO-05-365 Aviation Security 

would not remain in compliance with the congressional mandate to screen 

all checked baggage using EDS and ETD.25 However, because TSA would 

not identify these 27 airports, we were unable to determine whether these 

airports are among the 45 airports we identified as in the process of 

planning or constructing in-line systems. Table 8 identifies the nine 

airports awarded LOI agreements, total project costs, and the cost-share 

for the federal government and the airport. 

Table 8: Airports Awarded LOIs 

Airport 

Total 

project cost

Total federal 

cost-share 

(75 percent)

Airport costshare 

(25 percent) 

Estimated in-line 

operational date 

Atlanta $125.0 $93.8 $31.3 December 2005 

Boston 

116.0 87.0 29.0 

 Completed January 

2003 

Dallas-Fort Worth 139.2 104.4 34.8 June 2005 

Denver 95.0 71.2 23.8 January 2005 

Las Vegas 

(McCarran) 125.0 93.8 31.3 

 July 2005 

Los Angeles and 

Ontario, Calif. 341.9 256.5 85.4 

 September 2007 

Phoenix 122.0 91.5 30.5 Fall of 2006 

Seattle 212.0 159.0 53.0 March 2007 

Total $1,276.1 $957.1 $319.1 

Source: GAO analysis of TSA data. 

Note: Total project costs do not include costs to procure and install EDS machines. 

TSA officials stated that they also use other transaction agreements as an 

administrative vehicle to directly fund, with no long-term commitments, 

airport operators for smaller in-line airport modification projects.26 Under 

these agreements, as implemented by TSA, the airport operator also 

 25TSA officials stated that the number of airports that could benefit most from in-line 

checked baggage screening systems varies depending on changing airport circumstances, 

such as adding new terminals or an increased or decreased number of flights. 

26Other transaction agreements are administrative vehicles used by TSA to directly fund 

airport operators for smaller airport modification projects without undertaking a long-term 

commitment. These transactions take many forms and are generally not required to comply 

with federal laws and regulations that apply to contracts, grants, or cooperative 

agreements; and enable the federal government and others entering into these agreements 

to freely negotiate provisions that are mutually agreeable. 
Page 33 GAO-05-365 Aviation Security 

provides a portion of the funding required for the modification. As of 

September 30, 2004, TSA had negotiated arrangements with eight airports 

to fund small permanent in-line projects or portions of large permanent inline projects using other transaction agreements.27 These other transaction 

agreements range from about $640,000 to help fund the conceptual design 

of an in-line system for one terminal at the Dallas Fort-Worth airport to 

$37.5 million to help fund the design and construction of in-line systems 

and modification of the baggage handling systems for two terminals at the 

Chicago O’Hare International Airport. TSA officials stated that they would 

continue to use other transaction agreements to help fund smaller in-line 

projects.28

Airport operators also used the FAA’s Airport Improvement Program—

grants to maintain safe and efficient airports—in fiscal years 2002 and 

2003 to help fund facility modifications needed to accommodate installing 

in-line systems. As shown in table 7, 28 of 53 airports that reported either 

having constructed or planning to construct in-line systems relied on the 

Airport Improvement Program as their sole source of federal funding. 

 27The eight airports included four category X airports: Dallas Fort-Worth International, 

Chicago O’Hare International, Detroit Metro Wayne County, and San Francisco 

International; three category I airports: Piedmont Triad International (North Carolina), 

Pittsburgh International, and Sacramento International; and one category II airport 

Harrisburg International (Pennsylvania). These eight airports were among the 45 airports 

that we identified as being in the process of planning or constructing in-line systems. 

28TSA also used four other transaction agreements to fund work related to interim 

solutions, three of these agreements were for partial in-line systems that eventually were to 

be replaced by permanent in-line systems. 
Page 34 GAO-05-365 Aviation Security 

Airport officials at over half of the 45 airports that we identified are in the 

process of planning or constructing in-line systems stated that they will 

require federal funding in order to complete the planning and construction 

of these in-line systems. Despite this reported need, however, the 

President’s fiscal year 2005 and 2006 budget requests do not provide, and 

the fiscal year 2005 DHS Appropriations Act does not include, funding for 

additional LOIs for in-line EDS baggage screening systems beyond the 

eight already issued. Also, the availability of federal funds from the Airport 

Improvement Program for future planning and construction of in-line 

baggage screening systems is limited. In addition, perspectives differ 

regarding the appropriate role of the federal government, airport 

operators, and air carriers in funding these capital-intensive systems. 

Officials at 28 of the 45 airports that we identified in figure 5 as planning or 

constructing in-line baggage screening systems stated that they could not 

or would not move forward with installing these systems without funding 

support from TSA.29 Also, in our review of correspondence to TSA 

regarding 26 airports’ interest in receiving LOIs, officials from half of the 

26 airports stated that they would have to delay, suspend, or abandon their 

plans for installing in-line systems until TSA committed to funding these 

projects. According to TSA officials, the high cost of developing final 

design plans for in-line systems has resulted in airports delaying plans to 

install the systems until they are confident that TSA will be able to support 

their funding needs. 

Although airport officials stated that they will require federal funding to 

install in-line systems—and TSA officials reported that additional airports 

will require in-line systems to maintain compliance with the congressional 

mandate to screen 100 percent of checked baggage for explosives—TSA 

officials stated that they do not have sufficient resources in their budget to 

fund additional LOIs beyond the eight LOIs that have already been issued. 

Vision 100, among other things, provided for the creation of the Aviation 

Security Capital Fund to help pay for placing EDS machines in line with 

 29These 28 airports include 8 of the 9 airports that have been awarded LOIs by TSA for 

planning and constructing in-line systems. 

Airport Officials Report 

That They Will Require 

Federal Funding to Install 

In-line EDS Baggage 

Screening Systems, but the 

Availability of this Funding 

Is Uncertain, and 

Perspectives Differ 

Regarding Funding 

Responsibilities of the 

Federal Government and 

the Aviation Industry 
Page 35 GAO-05-365 Aviation Security 

airport baggage handling systems.30 However, according to OMB officials, 

the President’s fiscal year 2005 budget request, which referred to the 

Vision 100-mandated appropriation of $250 million for the Aviation 

Security Capital Fund, only supported continued funding for the eight LOIs 

that have already been issued and does not provide resources to support 

new LOIs for funding the installation of in-line systems at additional 

airports. Further, while the fiscal year 2005 DHS Appropriations Act 

provides $45 million for installing explosive detection systems in addition 

to the $250 million from the Aviation Security Capital Fund, Congress 

directed, in the accompanying conference report, that the $45 million be 

used to assist in the continued funding of the existing eight LOIs. Further, 

the President’s fiscal year 2006 budget request for TSA provides 

approximately $240.5 million for the continued funding of the eight 

existing LOIs and provides no funds for new LOI agreements for in-line 

system integration activities. 

In addition, the availability of Airport Improvement Program funds for 

airport security-related improvements, though expanded for a time, is 

presently limited as a resource for the installation of in-line EDS baggage 

screening systems. Following the events of September 11, ATSA 

authorized the use of Airport Improvement Program funds for securityrelated enhancements through fiscal year 2002. ATSA also provided for the 

use of Airport Improvement Program funds to replace airport baggage 

handling systems and to reconfigure airport terminal baggage areas as 

required to install explosive detection equipment, but Vision 100 amended 

this provision to allow only a specific portion of Airport Improvement 

Program funds to be used for this purpose after December 12, 2003.31

Subsequent prohibitions found in the fiscal year 2004 Consolidated 

 30Vision 100 authorizes up to $500 million for aviation security for each of fiscal years 2004 

through 2007, of which $250 million is a mandatory appropriation to the Aviation Security 

Capital Fund. Of that mandatory amount, the act designates $125 million as priority funding 

to fulfill intentions to obligate under LOIs. In the fiscal year 2004 Department of Homeland 

Security Appropriations Act, Congress provided $250 million for the physical modification 

of airports to install checked baggage explosive detection systems but did so separate from 

the Aviation Security Capital Fund because a provision of that act precluded the use of 

funds to establish the Fund in fiscal year 2004. The Intelligence Reform and Terrorism 

Prevention Act of 2004, Pub. L. No. 108-458, 118 Stat. 3638, enacted in December 2004, 

increases the authorized appropriation for aviation security from Vision 100 from $250 

million to $400 million for each of fiscal years 2005 through 2007. The $250 million 

mandatory appropriation remains the same. 

31Vision 100 limited the source of funding available to carry out this provision 

(49 U.S.C. § 47102(3)(b)(x)) to amounts apportioned under 49 U.S.C. § 47114. 
Page 36 GAO-05-365 Aviation Security 

Appropriations Act, enacted in January 2004, and again in the fiscal year 

2005 Consolidated Appropriations Act, enacted in December 2004, prohibit 

the use of Airport Improvement Program funds for activities related to the 

installation of in-line explosive detection systems. 

A 75 percent federal cost-share will apply to any project under an LOI for 

fiscal year 2005.32 Further, the President’s fiscal year 2006 budget request 

for TSA requests to maintain the 75 percent federal government cost share 

for projects funded by LOIs at large and medium airports. However, in 

testimony before Congress, an aviation industry official expressed a 

different perspective regarding the cost sharing between the federal 

government and the aviation industry for installing in-line checked 

baggage screening systems. Testifying in July 2004, the official said that 

airports contend that the cost of installing in-line systems should be met 

entirely by the federal government, given its direct responsibility for 

screening checked baggage, as established by law, in light of the national 

security imperative for doing so, and because of the economic efficiencies 

of this strategy. Although the official stated that airports have agreed to 

provide a local match of 10 percent of the cost of installing in-line systems 

at medium and large airports, as stipulated by Vision 100, he expressed 

opposition to the administration’s proposal, which was subsequently 

adopted by Congress for fiscal year 2005, to reestablish the airport’s costshare at 25 percent.33

In July 2004, the National Commission on Terrorist Attacks upon the 

United States (the 9/11 Commission) also addressed the issue of the 

federal government/airport cost-share for installing EDS in-line baggage 

 32The fiscal year 2003 Consolidated Appropriations Resolution authorized TSA to issue 

LOIs for terminal modifications related to the installation of in-line baggage screening 

systems and mandated that each LOI provide for a 75 percent federal cost-share of the 

project’s cost, with the remaining 25 percent to be paid by the airport operator at airports 

with at least 0.25 percent of the total number of passenger boardings each year at all 

airports (and 90 percent for projects at all other airports). Subsequently, Vision 100 

instituted a 90 percent federal cost-share of the project’s cost, with the remaining 

10 percent to be paid by the airport operator at medium and large hub airports (and 

95 percent for projects at any other airport) though TSA continued to operate at the 

75 percent cost-share. The fiscal year 2005 DHS Appropriations Act, signed into law in 

October 2004, reestablished the federal cost-share at 75 percent for any medium or large 

hub airport during fiscal year 2005. 

33TSA officials stated that the increased cost-share to 90 percent stipulated in Vision 100 

would further constrain their ability to fund future LOIs, as well as impact their ability to 

assist airports to achieve and maintain compliance with the congressional mandate to 

screen all checked baggage for explosives. 
Page 37 GAO-05-365 Aviation Security 

screening systems.34 Specifically, the commission recommended that TSA 

expedite the installation of in-line systems and that the aviation industry 

should pay its fair share of the costs associated with installing these 

systems, since the industry will derive many benefits from the systems. 

Although the 9/11 Commission recommended that the aviation industry 

should pay its fair share of the costs of installing in-line systems, the 

commission did not report what it believed the fair share to be.35

TSA has not conducted the analyses needed to plan for optimally 

deploying EDS and ETD equipment—including installing in-line EDS 

baggage screening systems or replacing ETD machines with stand-alone 

EDS machines—at the nation’s more than 400 airports to enhance security 

and reduce TSA staffing requirements and long-term costs. Although TSA 

established criteria to prioritize airport eligibility for receiving LOI funds 

for in-line EDS baggage screening systems, it has not conducted a 

systematic, prospective analysis to determine at which airports it could 

achieve long-term savings and enhanced security by installing in-line 

systems rather than continue to rely on labor-intensive stand-alone EDS 

and ETD machines to screen checked baggage for explosives. TSA’s 

retrospective analysis of the nine airports that received LOIs identified the 

potential for significant cost savings through the installation of in-line EDS 

baggage screening systems and the merit of conducting prospective 

analyses of other airports to provide information for future funding 

decisions. Further, for airports where in-line systems may not be 

economically justified because of the high cost of installing the systems, 

TSA has not conducted an analysis to determine whether it could achieve 

savings by making greater use of stand-alone EDS systems rather than 

relying on the use of more labor-intensive ETD machines. OMB has 

provided guidance for agencies to conduct these types of cost analyses to 

help build a business case for funding their programs. Moreover, Congress 

directed that TSA continue submitting plans for installing in-line baggage 

 34The 9/11 Commission Report: Final Report of the National Commission on Terrorist 

Attacks Upon the United States (Washington, D.C.: July 2004). 

35The Intelligence Reform and Terrorism Prevention Act of 2004 requires the Secretary of 

Homeland Security to conduct a cost-sharing study that must include, among other things, 

a proposed formula for cost sharing among the federal, state, and local governments and 

the private sector for projects to install in-line baggage screening equipment that reflects 

the benefits that each such entity will derive from the projects, including national security 

benefits and labor and other cost savings. 

TSA Has Not 

Systematically 

Planned for the 

Optimal Deployment 

of Checked Baggage 

Screening Equipment 

to Ensure the 

Efficient and CostEffective Screening 

for Explosives while 

Enhancing Security 

Benefits 
Page 38 GAO-05-365 Aviation Security 

screening systems. However, TSA has not yet provided Congress with all 

of the information requested. 

In October 2003, TSA reported to OMB criteria it used to prioritize airports 

eligible to receive LOI funds to install in-line EDS baggage screening 

systems. However, TSA did not systematically determine which airports 

could achieve long-term savings and improved security by installing in-line 

systems rather than continuing to rely on labor-intensive stand-alone EDS 

and ETD machines to screen checked baggage for explosives. 

The criteria TSA established for prioritizing airport participation in the LOI 

program, as shown in figure 6, included airports that were not yet 

conducting 100 percent screening of checked baggage with EDS or ETD, 

and airports that would fall out of compliance with the requirement to 

screen checked baggage with EDS or ETD at peak load times. In July 2004, 

TSA officials reported that they had recently expanded these criteria to 

take into account additional security benefits that an in-line baggage 

screening system would provide an airport. Specifically, TSA officials 

stated that they compared airport operational needs with identified 

threats, based on information received from TSA’s Transportation Security 

Intelligence Service, to consider security needs for specific airports. TSA 

officials further reported that an airport’s circumstances, such as 

passenger load increases or decreases, may change how it is prioritized, 

given these criteria, and that an airport could qualify to receive LOI 

funding based on more than one criterion. 

Figure 6: TSA Criteria for Prioritizing Letters of Intent 

TSA officials stated that they selected the first nine airports to receive 

LOIs to fund in-line baggage screening systems because, in general, they 

were the first to submit applications for an LOI, and they agreed to pay 

TSA Applied Criteria to 

Award Initial LOIs to Fund 

In-line Systems but Has 

Not Systematically 

Determined Which 

Additional Airports Should 

Receive Future In-line 

Systems to Increase 

Efficiencies and Enhance 

Security 

Fulfilling basic requirements:

(1) Airports not yet at 100 percent screening using explosive detection systems

(2) Airports that will fall out of compliance at peak loads because of seasonal fluctuations, air carrier moves, 

additions, and changes

DHS strategic investment projects:

(3) Airports with highly disruptive implementations and high staffing levels

(4) Airports with a heavy reliance on ETD machines that would benefit from improved operational efficiencies 

and cost reductions

Source: GAO analysis of TSA data.
Page 39 GAO-05-365 Aviation Security 

25 percent of airport modification costs in accordance with the LOI 

requirements.36 TSA officials also stated that the nine airports generally 

met their criteria even though seven of the airports had received LOIs in 

July and September 2003, before the TSA’s promulgation of the criteria in 

October 2003. 

In addition to the nine airports currently receiving LOI funds, TSA officials 

stated that, based on their criteria, in July 2004, they identified 

27 additional airports that are potential candidates for 22 future LOIs.37

TSA officials stated that an in-line screening system at each of these 

airports would provide enhanced security and efficiencies. More 

important, officials stated that if the 27 airports did not receive an LOI to 

install an in-line baggage system, these airports could fall out of 

compliance with the requirement to screen 100 percent of checked 

baggage using explosive detection systems during peak passenger traffic 

load periods or because of passenger load increases or new air carrier 

service—TSA’s second prioritization criterion shown in figure 6. Although 

TSA officials asserted that in July 2004, 27 airports were good candidates 

for in-line systems, they would not identify the 27 airports. TSA officials 

also did not provide the analyses they conducted to determine that these 

airports would fall out of compliance with the mandate to screen all 

checked baggage using explosive detection systems or state why these 

airports were more at risk than other airports for not complying with this 

mandate. Rather, TSA officials stated that they identified these 27 airports 

as good candidates for LOIs based on their day-to-day working knowledge 

of airports and professional judgment about airport operations. TSA 

officials were also unable to provide information on what the associated 

costs, benefits, and time frames would be for installing in-line systems at 

these 27 airports. 

Although TSA developed criteria to use as a guide for determining which 

airports should receive LOI funding for in-line EDS baggage screening 

systems, TSA has not yet conducted a systematic, prospective analysis of 

individual airports or groups of airports to determine at which airports 

installing in-line EDS systems would be cost-effective in terms of reducing 

long-term screening costs for the government and would improve security. 

 36TSA did not have a formal, standardized process for soliciting or responding to requests 

for LOIs. 

37LOI agreements can include multiple airports, as was the case with one of the original 

eight LOIs including both the Los Angeles International and Ontario airports. 
Page 40 GAO-05-365 Aviation Security 

Such an analysis would enable TSA to determine at which airports it 

would be most beneficial to invest limited federal resources for in-line 

systems rather than continue to rely on the stand-alone EDS and ETD 

machines to screen checked baggage for explosives, and it would be 

consistent with best practices for preparing benefit-cost analysis of 

government programs or projects called for by OMB Circular A-94.38 TSA 

officials stated that they have not conducted the analyses related to the 

installation of in-line systems at individual airports or groups of airports 

because they have used available staff and funding to ensure all airports 

have a sufficient number of EDS or ETD machines to meet the 

congressional mandate to screen all checked baggage with explosive 

detection systems. During the course of our review, in September 2004, 

TSA contracted for services through March 2005 to develop methodologies 

and criteria for assessing the effectiveness and suitability of airport 

screening solutions requiring significant capital investment, such as those 

projects associated with the LOI program. However, TSA officials could 

not provide us with information on how they plan to use the results of the 

effort in planning for the installation of in-line systems. 

In October 2004, the conference report accompanying the 2005 

Department of Homeland Security Appropriations Act directed that TSA 

continue submitting quarterly reports on its plans for the installation of inline baggage screening systems. However, TSA has not yet provided 

Congress with all of the information requested. Specifically, the 

conference report directed that TSA provide information describing, 

among other things, the universe of airports that could benefit from an inline EDS baggage screening system or other physical modifications; costs 

associated with each airport’s project, along with a tentative timeline for 

award and completion; and information reflecting the anticipated cost 

savings—particularly personnel savings—that would be achieved through 

the use of in-line checked baggage systems instead of ETD and stand-alone 

EDS systems. TSA, directed to provide a report on September 1, 2003, and 

every quarter thereafter, provided two reports to Congress. However, TSA 

was asked to submit amended reports because the original reports lacked 

the requested information. As of January 2005, TSA had not submitted the 

amended reports or subsequent reports to Congress. The conference 

report further directed TSA to develop a comprehensive plan for 

 38OMB Circular A-94 Guidelines and Discount Rates for Benefit-Cost Analysis of Federal 

Programs, January 22, 2002. Agencies use this guidance to support government decisions 

to initiate, review, or expand programs that would result in measurable costs or benefits 

extending for 3 or more years into the future. 
Page 41 GAO-05-365 Aviation Security 

expediting the installation of in-line EDS baggage screening systems, 

including the formulation of detailed budget requirements to provide for 

both equipment acquisition and the capital costs of installing these system 

configurations at airports. In addition, the December 2004, Intelligence 

Reform and Terrorism Prevention Act, among other things, directs TSA to 

develop a schedule to expedite the installation of in-line explosive 

detection systems. 

According to TSA officials, TSA recently began to conduct an analysis of 

alternatives to determine the best manner to acquire, deploy, and maintain 

EDS and ETD equipment for screening checked baggage as part of the 

Department of Homeland Security Investment Review process.39 However, 

according to TSA officials who prepared the review, the Investment 

Review Board review did not include a prioritization of which airports 

should receive funding for in-line systems or an analysis of screening 

needs at individual airports. TSA would not provide us with the baggage 

screening program data and analysis that it provided to the Investment 

Review Board for the review that occurred in late October 2004. 

Although TSA has not conducted a systematic analysis of cost savings and 

other benefits that could be derived from the installation of in-line baggage 

screening systems, TSA’s limited, retrospective cost-benefit analysis of inline projects at the nine airports with signed LOI agreements found that 

significant savings and other benefits may be achieved through the 

installation of these systems. This analysis was conducted in May 2004—

after the eight LOI agreements for the nine airports were signed in July 

and September 2003 and February 2004—to estimate potential future cost 

savings and other benefits that could be achieved from installing in-line 

systems instead of using stand-alone EDS systems. TSA estimated that inline baggage screening systems at these airports would save the federal 

government $1.3 billion40 compared with stand-alone EDS systems and that 

 39The Department of Homeland Security Investment Review Board reviews the 

department’s capital asset programs with acquisition costs exceeding $100 million to 

ensure that projects meet mission needs at the expected levels of cost and risk. 

40This figure refers to the net present value saved over 7 years if received up front. 

The Installation of In-line 

EDS Baggage Screening 

Systems May Result in 

Significant Savings and 

Benefits 
Page 42 GAO-05-365 Aviation Security 

TSA would recover its initial investment in a little over 1 year. 41 TSA’s 

analysis also provided data to estimate the cost savings for each airport 

over the 7-year period. According to TSA’s data, federal cost savings varied 

from about $50 million to over $250 million at eight of the nine airports, 

while at one airport, there was an estimated $90 million loss. The 

individual airport results are described in appendix IV. 

According to TSA’s analysis of the nine LOI airports, in-line cost savings 

critically depend on how much an airport’s facilities have to be modified 

to accommodate the in-line configuration. Savings also depend on TSA’s 

costs to buy, install, and network the EDS machines; subsequent 

maintenance cost; and the number of screeners needed to operate the 

machines in-line instead of using stand-alone EDS systems. In its analysis, 

TSA also found that a key factor driving many of these costs is 

throughput—how many bags an in-line EDS system can screen per hour 

compared with the rate for a stand-alone system. TSA used this factor to 

determine how many stand-alone EDS machines could be replaced by a 

single in-line EDS machine while achieving the same throughput. 

According to TSA’s analysis, in-line EDS would reduce by 78 percent the 

number of TSA baggage screeners and supervisors required to screen 

checked baggage at these nine airports, from 6,645 to 1,477 screeners and 

supervisors. However, the actual number of TSA screeners and supervisor 

positions that could be eliminated would be dependent on the individual 

design and operating conditions at each airport. 

TSA also reported that aside from increased efficiency and lower overall 

costs, there were a number of qualitative benefits that in-line systems 

would provide over stand-alone systems, including: 

• fewer on-the-job injuries, since there is less lifting of baggage when EDS 

machines are integrated into the airport’s baggage conveyor system; 

• less lobby disruption because the stand-alone EDS and ETD machines 

would be removed from airport lobbies; and 

• unbroken chain of custody of baggage because in-line systems are more 

secure, since the baggage handling is performed away from passengers. 

 41For a basis of comparison, Office of Management and Budget Circular A-94 stipulates 

using a 7 percent real discount rate to compute the present value of cost savings. TSA used 

a 4 percent real discount rate. Following Office of Management and Budget guidance, cost 

savings are $1.14 billion. In addition, in TSA’s analysis, the federal government does not pay 

for $319 million, or 25 percent, of project costs. Accounting for these costs to reflect total 

costs, as recommended by Circular A-94, lowers overall savings to $820 million. 
Page 43 GAO-05-365 Aviation Security 

TSA’s retrospective analysis of these nine airports indicates the potential 

for cost savings through the installation of in-line EDS baggage screening 

systems at other airports, and it provides insights about key factors likely 

to influence potential cost savings from using in-line systems at other 

airports. This analysis also indicates the merit of conducting prospective 

analyses of other airports to provide information for future federal 

government funding decisions as required by the OMB guidance on costbenefit analyses.42 This guidance describes best practices for preparing 

benefit-cost analysis of government programs or projects, one of which 

involves analyzing uncertainty. Given the diversity of airport designs and 

operations, TSA’s analysis could be modified to account for uncertainties 

in the values of some of the key factors, such as how much it will cost to 

modify an airport to install an in-line system. Analyzing uncertainty in this 

manner is consistent with OMB guidance. Appendix IV illustrates how 

analyzing uncertainty in TSA’s cost estimates can help identify which cost 

factors to focus on when determining the appropriateness of installing 

EDS baggage screening systems for a particular airport. 

TSA also has not systematically analyzed which airports could benefit 

from the implementation of additional stand-alone EDS systems in lieu of 

labor-intensive ETD systems at more than 300 airports that rely on ETD 

machines, and where in-line EDS systems may not be appropriate or costeffective. More specifically, TSA has not prepared a plan that prioritizes 

which airports should receive EDS machines (including machines that 

become surplus because of the installation of in-line systems) to balance 

short-term installation costs with future operational savings. Furthermore, 

TSA has not yet determined the potential long-term operating cost savings 

and the short-term costs of installing the systems, which are important 

factors to consider in conducting analyses to determine whether airports 

would benefit from the installation of EDS machines. TSA officials said 

that they had not yet had the opportunity to develop such analyses or 

plans, and they did not believe that such an exercise would necessarily be 

an efficient use of their resources, given the fluidity of baggage screening 

at various airports. 

There is potential for TSA to benefit from the introduction of smaller 

stand-alone EDS machines—in terms of labor savings and added 

efficiencies—at some of the more than 300 airports where TSA relies on 

 42OMB Circular A-94. 

TSA Has Not 

Systematically Assessed 

Needs of Airports to Gain 

Efficiencies by Making 

Greater Use of Stand-alone 

EDS Systems 
Page 44 GAO-05-365 Aviation Security 

the use of ETD machines to screen checked baggage. Stand-alone EDS 

machines are able to screen a greater number of bags in an hour than the 

ETD used for primary screening while lessening reliance on screeners 

during the screening process. For example, TSA’s analysis showed that an 

ETD machine can screen 36 bags per hour, while the stand-alone EDS 

machines can screen 120 to 180 bags per hour. As a result, it would take 

three to five ETD machines to screen the same number of bags that one 

stand-alone EDS machine could process. In addition, greater use of the 

stand-alone EDS machines could reduce staffing requirements. For 

example, one stand-alone EDS machine would potentially require 6 to 14 

fewer screeners than would be required to screen the same number of 

bags at a screening station with three to five ETD machines. This 

calculation is based on TSA estimates that 4.1 screeners are required to 

support each primary screening ETD machine, while one stand-alone EDS 

machine requires 6.75 screeners—including staff needed to operate ETD 

machines required to provide secondary screening. 

Without a plan for installing in-line EDS baggage screening systems, and 

for using additional stand-alone EDS systems in place of ETD machines at 

the nation’s airports, it is unclear how TSA will make use of new 

technologies for screening checked baggage for explosives, such as the 

smaller and faster EDS machines that may become available through 

TSA’s research and development programs. For example, TSA is working 

with private sector firms to enhance existing EDS systems and develop 

new screening technologies through its Phoenix project. As part of this 

project, in fiscal year 2003, TSA spent almost $2.4 million to develop a new 

computer-aided tomography explosives detection system that is smaller 

and lighter than systems currently deployed in airport lobbies. The new 

system is intended to replace systems currently in use, including larger 

and heavier EDS machines and ETD equipment. The smaller size of the 

system creates opportunities for TSA to transfer screening operations to 

other locations such as airport check-in counters. TSA certified this 

equipment in December 2004 and will pilot the machine in the field to 

evaluate its operational efficiency. Also, the ARGUS program was initiated 

in 1999 to develop EDS equipment that would cost less to build and 

install—even though baggage throughput may be lower—in order to 

provide a more uniform level of security using EDS machines at U.S. 

airports. TSA’s Transportation Security Laboratory has certified three 

varieties of these machines, though the machines have not been procured 

and deployed at U.S. airports. 

Without a Plan for 

Installing In-line Systems 

and EDS Equipment, It Is 

Unclear How TSA May 

Make Use of New 

Technologies to Screen 

Checked Baggage for 

Explosives 
Page 45 GAO-05-365 Aviation Security 

TSA has made substantial progress in installing EDS and ETD systems at 

the nation’s airports—mainly as part of interim lobby screening 

solutions—to provide the capability to screen all checked baggage for 

explosives, as mandated by Congress. With the objective of initially 

fielding this equipment largely accomplished, TSA needs to shift its focus 

from equipping airports with interim screening solutions to systematically 

planning for the more optimal deployment of checked baggage screening 

systems. The need for sound planning is also recognized by Congress 

through the Intelligence Reform and Terrorism Prevention Act of 2004 and 

through the fiscal year 2005 DHS Appropriations Act Conference Report, 

which, among other things, directs TSA to develop a comprehensive plan 

for expediting the installation of in-line explosive detection systems. Part 

of such planning should include analyzing which airports should receive 

federal support for in-line EDS baggage screening systems based on cost 

savings that could be achieved from more effective and efficient baggage 

screening operations and on other factors, including enhanced security. 

Also, for airports, where in-line systems may not be economically justified 

because of high investment costs, a cost effectiveness analysis could be 

used to determine the benefits of additional stand-alone EDS machines to 

screen checked baggage in place of the more labor-intensive ETD 

machines that are currently being used at the more than 300 airports. In 

addition, TSA should consider the costs and benefits of the new 

technologies being developed through its research and development 

efforts, which could provide smaller EDS machines that have the potential 

to reduce the costs associated with installing in-line EDS baggage 

screening systems or to replace ETD machines currently used as the 

primary method for screening. We believe that without such analyses, and 

without associated plans for the installation of in-line baggage screening 

systems and replacing stand-alone EDS machines, TSA cannot ensure that 

it is efficiently allocating its limited resources to maximize the 

effectiveness of its checked baggage screening operations. 

An analysis of airport baggage screening needs would also help enable 

TSA to determine whether expected reduced staffing costs, higher baggage 

throughput, and increased security would justify the significant up-front 

investment required to install in-line baggage screening. TSA’s 

retrospective analysis of nine airports installing in-line baggage screening 

systems with LOI funds, while limited, demonstrated that cost savings 

could be achieved through reduced staffing requirements for screeners 

and increased baggage throughput. In fact, the analysis showed that using 

in-line systems instead of stand-alone systems at these nine airports would 

save the federal government about $1 billion over 7 years and that TSA’s 

initial investment would be recovered in a little over 1 year. In considering 

Conclusions 
Page 46 GAO-05-365 Aviation Security 

airports for in-line baggage screening systems or the continued use of 

stand-alone EDS and ETD machines, a systematic analysis of the costs and 

benefits of these systems would help TSA justify the appropriate screening 

for a particular airport, and such planning would help support funding 

requests by demonstrating enhanced security, improved operational 

efficiencies, and cost savings to both TSA and the affected airport. 

In addition to identifying the most optimal baggage screening solutions at 

the nation’s airports, a systematic analysis of baggage screening 

operations and solutions—including an estimate of savings that could be 

achieved through the installation of in-line EDS baggage screening 

systems—would assist the Administration and Congress in determining 

the appropriate role of the federal government and aviation industry in 

funding capital-intensive in-line baggage screening systems. By identifying 

efficiencies that could be achieved for both TSA—such as savings 

achieved through reduced TSA staffing needs for screeners—and the 

airports and airlines—such as increased security due to less crowding in 

airport lobbies and the faster processing of baggage and passengers—the 

Administration and Congress would have information identifying the costs 

and benefits of in-line baggage screening systems for all parties involved to 

assist in determining an appropriate cost-share between the federal 

government and aviation industry in funding these systems. 

In developing the comprehensive plan for installing in-line EDS baggage 

screening systems, as directed by the fiscal year 2005 DHS Appropriation 

Act Conference Report, and in satisfying the requirements set forth in the 

Intelligence Reform and Terrorism Prevention Act of 2004, we recommend 

that the Secretary of the Department of Homeland Security direct the 

Administrator for the Transportation Security Administration to 

systematically assess the costs and benefits of deploying in-line baggage 

screening systems at airports that do not yet have in-line systems installed. 

As part of this assessment, the Administrator should take the following 

four actions: 

• identify and prioritize the airports where the benefits—in terms of cost 

savings of baggage screening operations and improved security—of 

replacing stand-alone baggage screening systems with in-line systems are 

likely to exceed the costs of the systems, or the systems are needed to 

address security risks or related factors; 

• consider the projected availability and costs of baggage screening 

equipment being developed through research and development efforts; 

Recommendations for 

Executive Action 
Page 47 GAO-05-365 Aviation Security 

• estimate total funds needed to install in-line systems where appropriate, 

including the federal funds needed given different assumptions regarding 

the federal government and airport cost-shares for funding the in-line 

systems; and 

• work collaboratively with airport operators, who are expected to share the 

costs and benefits of in-line systems, to collect data and prepare the 

analyses needed to develop plans for installing in-line systems. 

We also recommend that the Administrator for the Transportation Security 

Administration assess the feasibility, expected benefits, and costs of 

replacing ETD machines with stand-alone EDS machines for primary 

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

economically justified or justified for other reasons. In conducting this 

assessment, the Administrator should consider the projected availability 

and costs for screening equipment being developed through research and 

development efforts. 

We also made a recommendation to DHS addressing TSA’s protocols for 

screeners using ETD systems and associated screener training, which is 

included in the restricted versions of this report. 

We provided a draft of this report to DHS for review and comment. On 

February 18, 2005, we received written comments on the draft report, 

which are reproduced in appendix V.43 DHS generally concurred with our 

findings and recommendations, and agreed that efforts to implement the 

recommendations are critical to a successful checked baggage screening 

deployment program. Regarding our recommendation that TSA 

systematically assess the costs and benefits of deploying in-line baggage 

screening systems at airports that do not yet have in-line systems installed, 

DHS stated that TSA has initiated an analysis of deploying in-line checked 

baggage screening systems and is in the process of formulating criteria to 

use to identify those airports that would benefit from an in-line system. 

According to DHS, TSA believes that it can focus on approximately 40 

airports that handle anywhere from 60 to 80 percent of all checked 

 43 DHS’s initial comments on our draft report were dated January 12, 2005 , and we have 

included in the version of this report that contains classified and sensitive security 

information——GAO-05-135C—-and in our report containing sensitive security information 

but not the classified information——GAO-05-302SU. In its February18, 2005 letter, DHS

removed comments considered by TSA to be security sensitive information. 

Agency Comments 

and Our Evaluation 
Page 48 GAO-05-365 Aviation Security 

baggage nationwide. Once TSA officials have finalized the criteria and 

determined those airports at which in-line systems should be installed, 

they plan to conduct an airport-specific analysis to determine the 

individual costs and operational benefits. We are encouraged that TSA is 

proceeding with this analysis, which should provide a sound business case 

to justify resource allocation decisions. It is important, however, that TSA 

establish milestones and time frames for completing the analysis and 

documenting and reporting the results, such that they are available in a 

timely manner for DHS and congressional budget decisions. 

Concerning our recommendation that TSA assess the feasibility, expected 

benefits, and costs of replacing ETD machines with stand-alone EDS 

machines for primary screening at those airports where in-line systems 

would either not be economically justified or justified for other reasons, 

DHS stated that TSA has started conducting an analysis of the airports that 

rely on ETD machines as the primary checked baggage screening 

technology to identify those airports that would benefit from replacing 

ETDs with stand-alone EDS equipment. Again, we are pleased that TSA 

officials are conducting this analysis, which should provide them with the 

basis for optimizing the use of its EDS machines for screening checked 

baggage. Further, DHS stated that TSA continues to review and refine the 

protocols and training of all screening procedures including screening 

checked baggage, and are in the process of implementing the 

recommendations made by the DHS Inspector General regarding improved 

screener training and other improvements for both the passenger and 

checkpoint and checked baggage. 

TSA also provided additional technical comments on our draft report, 

which we have incorporated where appropriate. 

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

Homeland Security, the TSA Administrator, 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. 
Page 49 GAO-05-365 Aviation Security 

If you have any questions about this report, please contact me at 

(202) 512-3404, berrickc@gao.gov or Christine Fossett, Assistant Director 

at (202) 512-2956, fossettc@gao.gov. Key contributors to this report are 

listed in appendix VI. 

Cathleen A. Berrick, Director 

Homeland Security and Justice Issues 
Appendix I: Objectives, Scope, and 

Methodology 

Page 50 GAO-05-365 Aviation Security 

To assess efforts by the Transportation Security Administration (TSA) to 

screen checked baggage for explosives using explosives detection system 

(EDS) and explosives trace detection (ETD) equipment, we addressed the 

following questions: (1) How did TSA use the funds it initially budgeted to 

procure and install EDS and ETD systems and make associated airport 

modifications, and what was the impact of the initial deployment of EDS 

and ETD systems? (2) What actions are airports and TSA currently taking 

to install automated in-line EDS baggage screening systems,1

 and what are 

the federal resources that have been made available to fund these 

systems? (3) What actions, if any, is TSA taking to plan for the optimal 

deployment of in-line baggage screening systems in order to ensure the 

efficiency, cost effectiveness, and security of its checked baggage 

screening operations? 

To determine how TSA used its funding for procuring and installing EDS 

and ETD systems and modifying airports, we obtained and analyzed 

relevant legislation and appropriate budget documents, contracts, and 

inventory reports from TSA related to checked baggage screening with 

EDS and ETD machines. We interviewed TSA officials from the Office of 

Budget and Performance, the Office of Acquisition, and TSA’s Security 

Technology Deployment Office. We also obtained and reviewed funding 

and contractual documents from these locations. To determine what 

impact the initial deployment of EDS and ETD systems had on TSA and 

airport operations, we conducted a literature search to obtain information 

on the purpose and use of explosive detection screening equipment to 

screen checked baggage at airports for explosives. This search identified 

various TSA reports, Department of Homeland Security (DHS) Inspector 

General reports, Congressional Research Service reports, and aviation 

industry reports documenting TSA’s use of this equipment for screening 

checked baggage. Also, we obtained and reviewed relevant documents 

from TSA and interviewed TSA headquarters officials from TSA’s Office of 

Aviation Operations, Office of Chief Counsel, Office of Technology 

Deployment and Maintenance, and Office of Internal Affairs and Program 

Review. This documentation included information on staffing 

requirements and the number of bags per hour that can be screened by inline EDS systems as compared with stand-alone EDS and ETD machines. 

We also interviewed officials from TSA, air carriers, airports, explosive 

 1

In-line EDS checked baggage screening systems typically involve checked baggage 

undergoing automated screening while on a conveyor belt that sorts and transports 

baggage to the proper location for its ultimate loading onto an aircraft. 

Appendix I: Objectives, Scope, and 

Methodology 
Appendix I: Objectives, Scope, and 

Methodology 

Page 51 GAO-05-365 Aviation Security 

detection systems equipment manufacturers, and airport industry 

associations to obtain information regarding TSA’s efforts to improve 

checked baggage screening operations using EDS machines. Although we 

could not independently verify the reliability of all of this information, we 

compared it with other supporting documents, when available, to 

determine data consistency and reasonableness. Based on these efforts, 

we believe the information we obtained is sufficiently reliable for this 

report. Further, we reviewed the results from unannounced, undercover 

covert testing of checked baggage screening operations conducted by 

TSA’s Office of Internal Affairs and Program Review 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. 

To address our second and third objectives—to determine what actions 

airports and TSA are taking to develop in-line EDS baggage screening 

systems and what resources are available for these systems; and to 

determine what TSA is doing to optimally deploy these systems in order to 

improve the efficiency, cost effectiveness, and security of its checked 

baggage screening operations—we obtained briefings and other 

documents related to the planned use and installation of in-line systems 

and interviewed officials from the Office of Chief Counsel and the Office 

of Security Technology. We also interviewed officials from the TSA’s 

Transportation Security Laboratory in Atlantic City, New Jersey, to discuss 

the agency’s efforts to examine future baggage screening technologies and 

the certification process for EDS and ETD equipment. We also used 

information related to checked baggage screening from a Web-based 

survey of all 155 federal security directors about 263 of the airports under 

their supervision. This survey is described below. We also followed up by 

telephone with airport officials from 70 of those airports to obtain 

additional information about their plans for in-line systems. These airports 

were selected primarily based on the responses from the federal security 

directors regarding whether the airport had or planned on installing in-line 

EDS checked baggage screening systems. In addition, GAO’s Office of 

General Counsel formally requested that TSA describe its means for 

compliance with the baggage screening requirements of the Aviation and 

Transportation Security Act and the Homeland Security Act of 2002, and 

inquired how TSA would approach its letters of intent for funding in-line 

checked baggage screening systems in light of changes mandated by the 
Appendix I: Objectives, Scope, and 

Methodology 

Page 52 GAO-05-365 Aviation Security 

Vision 100—Century of Aviation Reauthorization Act.2 Also, to assess 

potential savings, we reviewed a TSA cost model showing savings 

expected to be achieved with in-line rather than stand-alone EDS 

equipment at nine airports. We assessed the model’s logic to ensure its 

completeness and correctness of calculations. Also, as discussed in 

appendix IV, we conducted a Monte Carlo simulation to: (1) illustrate 

sensitivity of potential cost savings of replacing stand-alone with in-line 

EDS systems to alternative values of key cost drivers and (2) to explore 

the variability in the key factors used by TSA in their model. Based on our 

review of TSA’s cost model, we believe that it is sufficiently reliable for the 

analyses we conducted and the information included in this report. 

In addition, in addressing all three objectives, we conducted site visits and 

a Web-based survey. Specifically, we conducted site visits at 

22 airports (12 category X airports, 9 category I airports, and 1 category II 

airport) to observe airport security baggage screening procedures and 

discuss issues related to the baggage screening processes with TSA, 

airport, and airline officials. We chose these airports on the basis of one or 

more of the following factors: a large number of passenger boardings; the 

existence of an operational in-line system; whether the airport had 

received or requested TSA funding for an in-line system; whether the 

airport had begun screening all checked baggage using EDS or ETD; and 

the proximity to a larger airport being visited by GAO. The results from 

our airport visits provide examples of checked baggage screening 

operations and issues but cannot be generalized beyond the airports 

visited because we did not use statistical sampling techniques in selecting 

the airports. We administered a Web-based survey to all 155 federal 

security directors who oversee security at each of the airports falling 

under TSA’s jurisdiction. The questionnaire contained questions related to 

the status of checked baggage screening operations and planning and 

implementation of in-line EDS checked baggage screening systems. A GAO 

survey specialist designed the questionnaire in combination with other 

GAO staff knowledgeable about airport security issues. We conducted 

pretest interviews with six federal security directors to ensure that the 

questions were clear, concise, and comprehensive. In addition, TSA 

managers and an independent GAO survey specialist reviewed the 

questionnaire. 

 2

The fiscal year 2005 Department of Homeland Security Appropriations Act re-established 

the federal cost-share for letters of intent at the pre-Vision 100 level. 
Appendix I: Objectives, Scope, and 

Methodology 

Page 53 GAO-05-365 Aviation Security 

For this Web-based survey, each federal security director received one or 

two airport-specific questionnaires to complete, depending on the number 

of airports for which he or she was responsible. Where a federal security 

director was responsible for more than two airports, we selected the first 

airport based on the federal security director’s location and the second 

airport to obtain a cross-section of all airports by size and geographic 

distribution. In all, we requested information on 265 airports. However, 

two airports were dropped from our initial selection because the airlines 

serving these airports suspended operations and TSA employees were 

redeployed to other airports. As a result, our sample size was reduced to 

263 airports, which included all 21 category X airports, 

60 category I airports, 49 category II airports, 73 category III airports, and 

60 category IV airports. In that we did not use probability sampling 

methods to select the sample of airports, we cannot generalize our 

findings beyond the selected airports in these categories. 

We conducted this Web-based survey from late March to mid-May 2004. 

We received completed questionnaires from all 155 federal security 

directors for all 263 separate airports for which we sought information for 

a 100 percent response rate. We called selected survey respondents, or 

other TSA officials designated to respond on the respondent’s behalf, to 

obtain answers to key survey questions that may have been left blank, to 

look into situations where instructions were not followed and to 

investigate answers that looked suspicious or out of range. The survey 

results are not subject to sampling errors because all federal security 

directors were asked to participate in the survey and we did not use 

probability sampling techniques to select specific airports. However, the 

practical difficulties of conducting any survey may introduce errors, 

commonly referred to as non-sampling errors. For example, 

inconsistencies in how a particular question is interpreted, in the sources 

of information that are available to respondents, or in how the data are 

entered into a database or were analyzed can introduce unwanted 

variability in the survey results. We took steps in the development of the 

questionnaires, the data collection, and the data editing and analysis to 

minimize these non-sampling errors. Also, in that these were Web-based 

surveys whereby respondents entered their responses directly into our 

database, data entry or transcription errors were possible. In addition, all 

computer programs used to analyze the data were peer-reviewed and 

verified to ensure that the syntax was written and executed correctly. 

We performed our work from September 2003 through January 2005 in 

accordance with generally accepted government auditing standards. 

Certain information we obtained and analyzed regarding explosive 
Appendix I: Objectives, Scope, and 

Methodology 

Page 54 GAO-05-365 Aviation Security 

detection technologies and their effectiveness in TSA’s checked baggage 

screening operations are classified or are considered by TSA to be 

sensitive security information. Accordingly, the results of our review of 

this information have been removed from this report. 3

 3

We issued two additional reports detailing the results of our review, which discuss results 

deemed to be classified or sensitive security information. The report that contains 

classified and sensitive security information is GAO, Aviation Security: Systematic 

Planning Needed to Optimize the Deployment of Checked Baggage Screening Systems, 

GAO-05-135C (Washington D.C.: February 4, 2005). The report containing sensitive security

information but not the classified information is GAO, Aviation Security: Systematic 

Planning Needed to Optimize the Deployment of Checked Baggage Screening Systems, 

GAO-05-302SU (Washington D.C.: February 4, 2005). 
Appendix II: Summary of Checked Baggage 

Screening Legislation 

Page 55 GAO-05-365 Aviation Security 

Table 9: Highlights of Authorizations in Laws Related to Checked Baggage Screening in Aviation Transportation Security 

since the Terrorist Attacks of September 11, 2001 

Authorizations found in public laws Key provisions 

Aviation and Transportation Security 

Act (ATSA), Pub. L. No. 107-71, 115 

Stat. 597 (Nov. 19, 2001) 

Established the Transportation Security Administration (TSA) as the agency responsible 

for security in all modes of transportation, including civil aviation 

 Appointed federal security managers to oversee the screening of passengers and 

baggage at airports 

 Deployment of federal personnel to screen all passengers and baggage at airports 

 Mandated the screening of all checked baggage with explosive detection systems by 

December 31, 2002, and authorized alternative means to screen checked baggage 

(positive passenger bag match, manual search, canine search in combination with other 

means, other technology approved by TSA) where explosive detections systems are 

unavailable 

 Mandated the imposition of passenger security fees (and authorized the imposition of air 

carrier fees, if necessary) 

 Authorized use of Airport Improvement Program funds to replace baggage conveyor 

systems and reconfigure terminal baggage areas for installing bulk explosive detection 

systems; for other security-related activities required by law or the Secretary of 

Transportation from September 11, 2001, through October 1, 2002; and waived the local 

matching share for fiscal 2002 security related projects 

 Required that the Computer-Assisted Passenger Prescreening System, or any successor 

system, evaluate all passengers before they board an aircraft and that procedures exist to 

ensure adequate screening of selected individuals and their checked baggage 

 Authorized $50 million for each of fiscal years 2002 through 2006 for research, 

development, testing and evaluation of technologies such as explosive detection systems 

Homeland Security Act of 2002, Pub. L. 

No. 107-296, 116 Stat. 2135 (Nov. 25, 

2002) 

Extended ATSA’s mandate to screen all checked baggage using explosive detection 

systems to December 31, 2003, for noncompliant airports and required that all baggage 

at noncompliant airports be screened by alternative means until the mandate is fulfilled 

 Requires the submission of a classified report describing TSA’s progress toward meeting 

the baggage screening mandate every 30 days to the Senate Committee on Commerce, 

Science and Transportation and the House of Representatives Committee on 

Transportation and Infrastructure 

 Requires the Secretary of Transportation to consult with the Secretary of Homeland 

Security before approving applications for Airport Improvement Program grants as they 

relate to security equipment or the installation of bulk explosive detection systems 

Consolidated Appropriations 

Resolution, 2003, Pub. L. No. 108-7, 117 

Stat. 386 (Feb. 20, 2003) 

Authorized $500 million for each of fiscal years 2003 through 2007 for TSA to issue letters 

of intent (LOIs) to airports, with a government cost-share of 75 percent at airports with at 

least 0.25 percent of total passenger boardings each at all airports (90 percent at any 

other airport) 

Emergency Wartime Supplemental 

Appropriations Act, 2003, Pub. L. No. 

108-11, 117 Stat. 559 (Apr. 16, 2003) 

Authorized LOIs to assist in the installation of explosive detection systems at airports by 

December 31, 2003 

Vision 100—Century of Aviation 

Reauthorization Act, Pub. L. No. 108-

176, 117 Stat. 2490 (Dec. 12, 2003) 

Limited the availability of Airport Improvement Program funds for replacing baggage 

conveyor systems and reconfiguring terminal baggage areas to install bulk explosive 

detection systems to entitlement funds 

Appendix II: Summary of Checked Baggage 

Screening Legislation 
Appendix II: Summary of Checked Baggage 

Screening Legislation 

Page 56 GAO-05-365 Aviation Security 

Authorizations found in public laws Key provisions 

 Required the Secretary of Homeland Security to study the effectiveness of the aviation 

security system, including checked baggage, and to report that study within 6 months of 

the act’s passage to the Senate Committee on Commerce, Science and Transportation 

and the House of Representatives Committee on Transportation and Infrastructure 

 Authorized TSA to make grants for projects to replace baggage conveyer systems related 

to aviation security, to reconfigure terminal baggage areas as needed to install explosive 

detection systems, to enable TSA to deploy explosive detection systems behind the ticket 

counter, in the baggage sorting area, or in line with the baggage handling system, and for 

other airport security capital improvement projects TSA determines will improve security 

at an airport or improve the efficiency of the airport without lessening security 

 Authorized up to $500 million for each of fiscal years 2004 through 2007 for TSA to make 

grants under 49 U.S.C. § 44923: 

$250 million mandatory appropriation derived from passenger security fees to constitute 

the Aviation Security Capital Fund: $125 million available on the basis of airport size and 

aviation security risks; $125 million available for discretionary grants with priority to 

fulfilling LOIs 

$250 million authorized appropriation for each of fiscal years 2004 through 2007: 50 

percent available on the basis of airport size and aviation security risks; 50 percent 

available for discretionary grants with priority to fulfilling LOIs 

 Authorizes LOIs for airport security improvement projects at a 90 percent government 

cost-share at medium or large hub airports (95 percent at any other airport) and provides 

that TSA shall revise LOIs issued before the date of enactment to reflect the new costshare with respect to grants made after September 30, 2003 

Intelligence Reform and Terrorism 

Prevention Act of 2004, Pub. L. No. 

108-458, 118 Stat. 3638 (Dec. 17, 2004) 

Requires that TSA take action to expedite the installation and use of baggage screening 

equipment and requires that TSA submit schedules to the Senate Committee on 

Commerce, Science and Transportation and the House of Representatives Committee on 

Transportation and Infrastructure for expediting the installation and use of in-line baggage 

screening equipment that estimate the impact that such equipment, facility modification, 

and baggage conveyor placement will have on staffing needs and levels related to 

aviation security and for replacing trace detection equipment with explosive detection 

system equipment as soon as practicable and where appropriate, within 180 days of 

enactment 

 Requires the Secretary of Homeland Security, in consultation with air carriers, airport 

operators, and other interested parties, to submit, in conjunction with its fiscal year 2006 

budget proposal, a proposed formula for cost sharing among federal, state and local 

governments and the private sector for the installation of in-line baggage screening 

systems, recommendations for defraying the costs of in-line systems, and a review of 

innovative financing approaches and possible cost savings associated with installing inline systems at airports 

 Amends 49 U.S.C. § 44923(i) by increasing the authorized appropriations for each of 

fiscal years 2005 through 2007 to $400 million 

 Allows for a reimbursement period under any LOI to extend for a maximum of 10 years 

after issuance 

Source: GAO analysis of public laws related to checked baggage screening since the Terrorist Attacks of September 11, 2001. 
Appendix II: Summary of Checked Baggage 

Screening Legislation 

Page 57 GAO-05-365 Aviation Security 

Table 10: Highlights of Appropriations in Laws Related to Checked Baggage Screening in Aviation Transportation Security 

since the Terrorist Attacks of September 11, 2001 

Appropriations found in public laws Funding appropriated and other key provisions 

2002 Emergency Supplemental 

Appropriations Act for Recovery from and 

Response to Terrorist Attacks on the 

United States, Pub. L. No. 107-38, 115 Stat. 

220 (Sept. 18, 2001) 

$40 billion (available until expended) for, among other things, the costs of providing 

increased transportation security; no specific baggage screening-related appropriation

Department of Transportation and Related 

Agencies Appropriations Act, Pub. L. No. 

107-87, 115 Stat. 833 (Dec. 18, 2001) 

$1.25 billion (available until expended) for necessary expenses of TSA related to 

providing civil aviation security services pursuant to ATSA; no specific baggage 

screening-related appropriation 

 H.R. Conf. Rep. No. 107-308 (2001) directed $97.5 million from “FAA, Facilities and 

Equipment”: $38 million for bulk explosive detection systems; $12 million for trace 

detection equipment; $12 million for threat image projection systems; $2 million for 

computer-based training; $33.5 million for system integration 

Department of Defense Emergency 

Supplemental Appropriations for Recovery 

from and Response to Terrorist Attacks on 

the United States, 2002; Department of 

Defense Appropriations Act, 2002, Pub. L. 

No. 107-117, 115 Stat. 2230 (Jan. 10, 2002) 

Funds to be obligated from amounts made available in Public Law 107-38: 

$108.5 million to “FAA Facilities and Equipment” (available until Sept. 30, 2004) for 

procurement and installation of explosive detection systems 

$50 million to “FAA Research and Development” (available until Sept. 30, 2003), of 

which H.R. Conf. Rep. No. 107-350 (2001) directed $2 million for a demonstration of 

100 percent positive passenger bag match technology at DCA 

2002 Supplemental Appropriations Act for 

Further Recovery from and Response to 

Terrorist Attacks on the United States, Pub. 

L. No. 107-206, 116 Stat. 820 (Aug. 2, 2002) 

$738 million (available until expended) for physical modifications to commercial 

service airports for installing checked baggage explosive detection systems 

Consolidated Appropriations Resolution, 

2003, Pub. L. No. 108-7, 117 Stat. 386 

(Feb. 20, 2003) 

$3.0379 billion (available until expended) for screening activities, of which H.R. Conf. 

Rep. No. 108-10 (2003) directed $1.4159 billion for baggage screening activities: 

The Resolution earmarked $265 million for the physical modification of commercial 

service airports to install, and $174.5 million for the procurement of, checked baggage 

explosive detection systems 

The Conference Report directed $900 million for baggage screeners, $75 million for 

detection equipment maintenance, and $1.4 million for a checked baggage data 

system 

Emergency Wartime Supplemental 

Appropriations Act, 2003, Pub. L. No. 

108-11, 117 Stat. 559 (Apr. 16, 2003). 

$235 million (available until expended) for the physical modification of commercial 

service airports to install checked baggage explosive detection systems 

Department of Homeland Security 

Appropriations Act, 2004, Pub. L. No. 

108-90, 117 Stat. 1137 (Oct. 1, 2003). 

$1.3187 billion (available until expended) for baggage screening activities: 

The act earmarked $250 million for physical modification of commercial service 

airports to install, and $150 million for the procurement of, checked baggage 

explosive detection systems. 

H.R. Conf. Rep. No. 108-280 (2003) directed $774.2 million for personnel, 

compensation and benefits; $69.5 for training and other purposes; and $75 million for 

explosive detection system maintenance 

 $45 million (available until expended) for research and development of explosive 

detection devices 
Appendix II: Summary of Checked Baggage 

Screening Legislation 

Page 58 GAO-05-365 Aviation Security 

Appropriations found in public laws Funding appropriated and other key provisions 

 Precludes the obligation or expenditure of funds appropriated or otherwise made 

available by this or any other act to carry out provisions of 49 U.S.C. § 44923(h)—the 

Aviation Security Capital Fund—during fiscal year 2004 

Consolidated Appropriations Act, 2004, 

Pub. L. No. 108-199, 118 Stat. 3 (Jan. 23, 

2004) 

Precludes the availability of Airport Improvement Program funds for the replacement 

of baggage conveyor systems, reconfiguration of terminal baggage areas, and other 

improvements necessary to install bulk explosive detection systems 

Department of Homeland Security 

Appropriations Act, 2005, Pub. L. No. 108-

334, 118 Stat. 1298 (Oct.18, 2004) 

$1.45246 billion (available until expended) for baggage screening activities: 

The act earmarks $180 million for procurement of, and $45 million to install, checked 

baggage explosive detection systems. 

H.R. Conf. Rep. 108-774 (2004) directs $848.86 million for personnel, compensation 

and benefits; $203.66 million for training and other purposes; $174.94 million for 

maintenance; and at least $30 million of the $180 procurement earmark to install nextgeneration explosive detection systems to permit more efficient handling of checked 

bags and reduce dependence on baggage screeners, particularly at medium-sized 

and small airports. It further recognizes the mandatory $250 million mandatory 

appropriation to the Aviation Security Capital Fund. 

 $54 million earmarked for research and development of next generation explosive 

detection devices, of which the Conference Report directs $10 million for the 

Manhattan II project 

 Reestablishes, for fiscal year 2005, the75 percent government cost-share for the eight 

LOIs issued for the installation of in-line baggage screening systems 

 The Conference Report directs that TSA: 

comprehensively plan for expediting the installation of in-line explosive detection 

systems, including the formulation of detailed budget requirements to provide for both 

equipment acquisition and the capital costs of installing such system configurations at 

airports; continue submitting quarterly reports, consistent with the requirement of H.R. 

Rep. No. 108-169 (2003), on its plans for the installation of in-line systems 

Consolidated Appropriations Act, 2005, 

Pub. L. No. 108-447, 118 Stat. 2809 (Dec. 8, 

2004) 

Precludes the availability of Airport Improvement Program funds for the replacement 

of baggage conveyor systems, reconfiguration of terminal baggage areas, and other 

improvements necessary to install bulk explosive detection systems 

Source: GAO analysis of public laws related to checked baggage screening since the Terrorist Attacks of September 11, 2001. 
Appendix III: Airports Receiving TSA Airport 

Modification and EDS/ETD Equipment 

Installation Funding for In-line Systems 

Page 59 GAO-05-365 Aviation Security 

Table 11: Listing of Airports Receiving Modification and EDS/ETD Equipment Installation Funding for Developing In-line EDS 

Baggage Screening Systems as of September 30, 2004 

Name of airport 

LOI funding for 

airport modification 

Other transaction 

agreement funding for 

airport modification 

Airport modification and EDS 

equipment installation work 

performed by Boeing Service 

Company, other contractors, or 

EDS manufacturers 

13 Category X Airports 

Hartsfield Atlanta International X 

Boston Logan International X X 

Baltimore/Washington International X 

Chicago O’Hare International X 

Denver International X X 

Dallas-Fort Worth International X X X 

Detroit Metro Wayne County X 

Houston George Bush Intercontinental X 

Los Angeles International X 

Miami International X 

Orlando International X 

San Francisco International X X 

Seattle-Tacoma International X X 

Subtotal 6 4 9 

16 Category I Airports 

Anchorage Ted Stevens International X 

Boise Air Terminal/Gowen Field X 

Burbank-Glendale-Pasadena X 

Santa Ana John Wayne X 

Las Vegas McCarran International X X 

Metropolitan Oakland International Airport X 

Oklahoma City Will Rogers World X 

Ontario International X 

Phoenix Sky Harbor International X 

Greensboro Piedmont Triad International X 

Pittsburgh International X X 

Sacramento International X 

Southwest Florida International 

Spokane International X 

Tampa International X 

Tulsa International X 

Appendix III: Airports Receiving TSA Airport 

Modification and EDS/ETD Equipment 

Installation Funding for In-line Systems 
Appendix III: Airports Receiving TSA Airport 

Modification and EDS/ETD Equipment 

Installation Funding for In-line Systems 

Page 60 GAO-05-365 Aviation Security 

Name of airport 

LOI funding for 

airport modification 

Other transaction 

agreement funding for 

airport modification 

Airport modification and EDS 

equipment installation work 

performed by Boeing Service 

Company, other contractors, or 

EDS manufacturers 

Subtotal 3 3 12 

3 Category II Airports 

Harrisburg International X X 

Juneau International X 

Manchester X 

Subtotal 1 3 

1 Category III Airport 

Okaloosa County Air Terminal X 

Subtotal 1 

Total (33 Airports) 9 8 25 

Source: GAO analysis of TSA obligation and commitment data and contract files. 
Appendix IV: Analysis of TSA’s Cost Savings 

Estimates for In-line EDS Checked Baggage 

Screening Systems 

Page 61 GAO-05-365 Aviation Security 

TSA estimated that baggage screening operations at the nine airports 

receiving letters of intent (LOIs) will result in a savings to the federal 

government of $1.26 billion over 7 years—and would recover the initial 

investment in 1.07 years—as a result of installing in-line rather than standalone EDS systems.1

 To make these estimates, TSA made a variety of 

assumptions about in-line and stand-alone EDS systems, including how 

many bags can be processed per hour by both, how many screeners both 

would need, and how much it would cost to purchase, install, and operate 

these systems.2

 In addition, TSA used data on how much it cost to modify 

these nine airports to accommodate in-line systems. In considering the 

accuracy of TSA’s estimates, uncertainties inherent in many of these 

assumptions should be considered. TSA could have analyzed uncertainty 

in their estimate by conducting sensitivity or other analyses to determine 

how variations in these assumptions would change its estimate of cost 

savings. Analyzing uncertainty in this way is consistent with best practices 

for preparing benefit-cost analysis of government programs or projects 

called for by OMB Circular A-94. Nonetheless, TSA’s cost model for these 

nine airports offers insights about key factors likely to influence potential 

cost savings at other airports. 

To illustrate taking uncertainty into account, we conducted a Monte Carlo 

analysis using TSA’s cost model.3

 We found that TSA’s cost savings 

estimate of $3.5 million per in-line EDS machine as compared to standalone could range from a loss of $1.6 million to a savings of $8.3 million 

per machine using generalized assumptions about cost uncertainty in 

TSA’s model. The most important source of uncertainty causing this wide 

range in possible savings was the cost to modify an airport to 

accommodate an in-line EDS system. Variation in modification costs 

explained over 60 percent of the variation in potential cost savings from 

 1

This is the present value of cost savings over a seven-year period. Unless otherwise noted, 

all dollar figures cited are present values. As noted earlier, this estimate falls to 

$1.14 billion after adjustments to the discount rate following Office of Management and 

Budget Circular A-94 guidance. 

2

Costs to install and multiplex in-line EDS systems were based on budget assumptions 

rather than true requirements. 

3

Our analysis was conducted using what is called Monte Carlo simulation, which uses 

random numbers to measure the effects of uncertainty. In the absence of additional 

information, our simulation is based on some general assumptions about the probability 

distributions characterizing values used by TSA for most of the cost factors. In the case of 

modification costs, we were able to use information on the variation of those costs across 

the nine airports. 

Appendix IV: Analysis of TSA’s Cost Savings 

Estimates for In-line EDS Checked Baggage 

Screening Systems 
Appendix IV: Analysis of TSA’s Cost Savings 

Estimates for In-line EDS Checked Baggage 

Screening Systems 

Page 62 GAO-05-365 Aviation Security 

in-line EDS as compared to stand-alone EDS. The next most important 

variable, the number of bags per hour that in-line and stand-alone 

machines can screen per hour, each accounted for about 15 percent of the 

variation in cost savings. In this way, Monte Carlo analysis can offer 

insights on factors to focus on when determining the appropriateness of 

an in-line EDS baggage screening system for a particular airport.4

The analysis provided by TSA aggregated the nine airports to present a 

total estimate. Using TSA’s analysis, we were able to determine the results 

for each of the nine airports. Figure 7 illustrates the variation in 

modification costs at the nine airports TSA studied, ranging from over 

$14 million per in-line EDS machine at Seattle to less than $2 million for 

Boston and Dallas-Fort Worth.5

 Figure 8, which shows the cost savings 

from in-line EDS compared to stand-alone EDS, identifies that Seattle 

could end up spending more for an in-line EDS system than from using 

stand-alone EDS machines. Further, as shown in figure 9, at Seattle the 

relatively large costs for upfront in-line EDS are not offset by the 

estimated $48 million in operation and maintenance cost savings; 

therefore, the in-line EDS system may be more costly than EDS standalone. By contrast, at Dallas-Fort Worth, the upfront costs of in-line EDS 

are lower than for stand-alone EDS, and there is an estimated $252 million 

in operation and maintenance cost savings. Therefore, the in-line EDS 

system at Dallas-Fort Worth may be less costly than stand-alone EDS. 

 4

TSA’s model covers nine airports handling relatively large numbers of passengers, 

reflecting the fact that in-line EDS has been limited mostly to larger airports. 

5

TSA’s data shows zero cost shown for Ontario, but it may be due to it being combined with 

Los Angeles. 
Appendix IV: Analysis of TSA’s Cost Savings 

Estimates for In-line EDS Checked Baggage 

Screening Systems 

Page 63 GAO-05-365 Aviation Security 

Figure 7: Airport Modification Costs Per In-line EDS Machine at Nine Airports 

0

2,000,000

4,000,000

6,000,000

8,000,000

10,000,000

12,000,000

14,000,000

16,000,000

Dollars

Source: Transportation Security Administration data.

Airports

0

Los

Angeles

Seattle Las

Vegas

Dallas

Fort

Worth

Atlanta Boston Denver Phoenix Ontario
Appendix IV: Analysis of TSA’s Cost Savings 

Estimates for In-line EDS Checked Baggage 

Screening Systems 

Page 64 GAO-05-365 Aviation Security 

Figure 8: Cost Savings from In-line EDS Systems Compared to Stand-alone EDS at 

Nine Airports 

-150,000,000

-100,000,000

-50,000,000

0

50,000,000

100,000,000

150,000,000

200,000,000

250,000,000

300,000,000

Present value

Source: Transportation Security Administration data.

Airports

Los

Angeles

Seattle Las

Vegas

Dallas

Fort

Worth

Atlanta Boston Denver Phoenix Ontario
Appendix IV: Analysis of TSA’s Cost Savings 

Estimates for In-line EDS Checked Baggage 

Screening Systems 

Page 65 GAO-05-365 Aviation Security 

Figure 9: Costs and Savings at Nine Airports 

-200,000,000

-150,000,000

-100,000,000

-50,000,000

0

50,000,000

100,000,000

150,000,000

200,000,000

250,000,000

300,000,000

Dollars

Source: Transportation Security Administration data.

Airports

Los

Angeles

Seattle Los

Vegas

Dallas

Fort

Worth

Atlanta Boston Denver Phoenix Ontario

In-line operation and maintenance cost savings 

Upfront standalone EDS costs minus upfront in-line EDS costs 

Overall savings from in-line
Appendix V: Comments from the Department 

of Homeland Security 

Page 66 GAO-05-365 Aviation Security 

Appendix V: Comments from the Department 

of Homeland Security 
Appendix V: Comments from the Department 

of Homeland Security 

Page 67 GAO-05-365 Aviation Security 
Appendix V: Comments from the Department 

of Homeland Security 

Page 68 GAO-05-365 Aviation Security 
Appendix VI: GAO Contacts and Staff 

Acknowledgments 

Page 69 GAO-05-365 Aviation Security 

Cathleen A. Berrick (202) 512-3404 

Christine A. Fossett (202) 512-2956 

In addition to those named above, David Alexander, Leo Barbour, 

Charles Bausell Jr., Kevin Copping, Katherine Davis, Kevin Dooley, 

David Hooper, Lemuel Jackson, Stuart Kaufman, Noel Lance, 

Thomas Lombardi, Jan Montgomery, Jobenia Odum, Jean Orland, 

Keith Rhodes, Minette Richardson, and Mark Tremba were key 

contributors to this report. 

Appendix VI: GAO Contacts and Staff 

Acknowledgments 

GAO Contacts 

Staff 

Acknowledgments 
Glossary 

Page 70 GAO-05-365 Aviation Security 

TSA classifies the over 400 airports in the United States that require 

screening into one of five categories (X, I, II, III, and IV) based on various 

factors, such as the total number of take-offs and landings annually, the 

extent to which passengers are screened at the airport, and other special 

security considerations. In general, category X airports have the largest 

number of passenger boardings and category IV airports have the smallest. 

TSA periodically reviews airports in each category, and, if appropriate, 

changes an airport’s categorization to reflect current operations. 

The Airport Improvement Program has provided federal grants since the 

passage of the Airport and Airway Improvement Act of 1982, Pub. L. No. 

97-248, 96 Stat. 324. Administered by the Federal Aviation Administration, 

Airport Improvement Program grants have supported airport planning and 

development. Grants are issued to maintain and enhance airport safety, 

preserve existing airport infrastructure, and expand capacity and 

efficiency throughout the airport system. Funds obligated for the Airport 

Improvement Program are drawn from the Airport and Airway Trust Fund, 

which is supported by user fees and fuel taxes. 

An individual’s personal property offered to and accepted by an aircraft 

operator for transport, which will be inaccessible to the individual during 

flight. 

A program is cost effective if, on the basis of life cycle cost analysis of 

competing alternatives, it is determined to have the lowest costs 

expressed in present value terms for a given amount of benefits. Costeffectiveness analysis is appropriate whenever it is unnecessary or 

impractical to consider the dollar value of the benefits provided by the 

alternatives under consideration. This is the case whenever (1) each 

alternative has the same annual benefits expressed in monetary terms; or 

(2) each alternative has the same annual affects but dollar values cannot 

be assigned to their benefits. 

A TSA certified automated device that has the ability to detect in checked 

baggage, the amounts, types, and configurations of explosive material 

specified by the TSA. An EDS machine uses computer-aided tomography 

to automatically measure the density of objects in baggage to determine 

whether the objects have the same density as explosives. The system 

automatically triggers an alarm when objects with high densities 

characteristic of explosives are detected. 

Glossary 

Airport categories 

Airport Improvement 

Program 

Checked baggage 

Cost-effectiveness analysis 

Explosives Detection 

System (EDS) 
Glossary 

Page 71 GAO-05-365 Aviation Security 

A device that has been certified by TSA for detecting explosive vapors and 

residues on objects intended to be transported aboard an aircraft. 

Explosives trace detection works by detecting vapors and residues of 

explosives. Human operators collect samples by rubbing bags with swabs, 

which are chemically analyzed to identify any traces of explosive 

materials. ETD is used both for primary screening of baggage and 

secondary screening to resolve alarms from EDS machines. 

Solutions employed by TSA to initially deploy explosive detection systems 

to screen 100 percent of checked baggage for explosives, until more 

permanent solutions could be designed and constructed. Efforts involved 

designing and implementing facility modifications, such as new 

construction, infrastructure reinforcement, and modification of electrical 

systems required to install the EDS and ETD equipment; and developing 

and administering equipment training for baggage screeners. 

A baggage conveyor system with incorporated EDS machines. The EDS’s 

baggage feed and output belts are directly connected to an airline’s or 

airport’s baggage belt system. The checked baggage undergoes automated 

screening in the EDS while on the conveyor belt system that sorts and 

transports baggage to the proper location for its ultimate loading on an 

aircraft. Baggage is introduced into the EDS without manual loading or 

unloading by TSA screeners. 

The fiscal year 2003 Consolidated Appropriations Resolution, Pub. L. No. 

108-7, 117 Stat. 11, authorized an LOI program for shared federal 

government and aviation industry funding to support facility modification 

costs associated with the installation of in-line EDS baggage screening 

systems. The Vision 100—Century of Aviation Reauthorization Act, Pub. L. 

No. 108-176, 117 Stat. 2490 (2003), also authorized the use of LOIs for this 

purpose. 

EDS machines are networked together so that images from multiple EDS 

machines can be sent to a centralized location where screeners can 

resolve alarms by studying EDS generated images. 

When an EDS machine alarms, indicating the possibility of explosives, 

TSA screeners, by reviewing computer generated images of the inside of 

the bag, attempt to determine whether or not a suspect item or items are 

in fact explosive materials. If the screener is unable to make this 

determination, the bag is diverted from the main conveyor belt into an 

area where it receives a secondary screening by a screener with an ETD 

machine. 

Explosives Trace 

Detection (ETD) 

Interim lobby 

solutions 

In-line system (also known 

as integrated checked 

baggage screening system 

or integrated EDS system) 

Letters of intent (LOI) 

Multiplex 

On-screen alarm resolution 

of EDS alarms 
Glossary 

Page 72 GAO-05-365 Aviation Security 

Other transaction agreements are administrative vehicles used by TSA to 

directly fund airport operators for smaller in-line airport modification 

projects without undertaking a long-term commitment. These 

transactions, which undertake many forms and are generally not required 

to comply with Federal laws and regulations that apply to contracts, 

grants, and/or cooperative agreements, enable the federal government and 

others entering into these agreements to freely negotiate provisions that 

are mutually agreeable. 

An alternative means of screening checked baggage, conducted by the 

airline, which requires that the passenger be on the same aircraft as his or 

her checked baggage. 

EDS machines that are placed in terminal lobbies, curbside or in baggage 

makeup areas, not integrated with baggage conveyor systems as part of inline systems. 

Bags screened per hour as a measure of efficiency. 

Other Transaction 

Agreements 

Positive passenger 

bag match 

Stand-alone EDS machines 

Throughput 

(440386) 
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