United States Government Accountability Office

GAO Report to Congressional Requesters

AVIATION SECURITY

Risk, Experience, and 

Customer Concerns 

Drive Changes to 

Airline Passenger 

Screening Procedures, 

but Evaluation and 

Documentation of 

Proposed Changes 

Could Be Improved 

April 2007 

 

GAO-07-634 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

April 2007

AVIATION SECURITY

Risk, Experience, and Customer 

Concerns Drive Changes to Airline 

Passenger Screening Procedures, but 

Evaluation and Documentation of 

Proposed Changes Could Be Improved 

Highlights of GAO-07-634, a report to 

congressional requesters 

The Transportation Security 

Administration’s (TSA) most visible 

layer of commercial aviation 

security is the screening of airline

passengers at airport checkpoints,

where travelers and their carry-on 

items are screened for explosives

and other dangerous items by

transportation security officers 

(TSO). Several revisions made to

checkpoint screening procedures 

have been scrutinized and

questioned by the traveling public

and Congress in recent years. 

For this review, GAO evaluated 

(1) TSA’s decisions to modify 

passenger screening procedures 

between April 2005 and December 

2005 and in response to the alleged

August 2006 liquid explosives 

terrorist plot, and (2) how TSA 

monitored TSO compliance with

passenger screening procedures. 

To conduct this work, GAO

reviewed TSA documents, 

interviewed TSA officials and 

aviation security experts, and 

visited 25 airports of varying sizes

and locations. 

Between April 2005 and December 2005, proposed modifications to 

passenger checkpoint screening standard operating procedures (SOP) were 

made for a variety of reasons, and while a majority of the proposed 

modifications—48 of 92—were ultimately implemented at airports, TSA’s 

methods for evaluating and documenting them could be improved. SOP 

modifications were proposed based on the professional judgment of TSA 

senior-level officials and program-level staff. TSA considered the daily 

experiences of airport staff, complaints and concerns raised by the traveling 

public, and analysis of risks to the aviation system when proposing SOP 

modifications. TSA also made efforts to balance the impact on security,

efficiency, and customer service when deciding which proposed 

modifications to implement, as in the case of the SOP changes made in 

response to the alleged August 2006 liquid explosives terrorist plot. In some 

cases, TSA tested proposed modifications at selected airports to help 

determine whether the changes would achieve their intended purpose. 

However, TSA’s data collection and analyses could be improved to help TSA 

determine whether proposed procedures that are operationally tested would 

achieve their intended purpose. For example, TSA officials decided to allow 

passengers to carry small scissors and tools onto aircraft based on their 

review of threat information, which indicated that these items do not pose a 

high risk to the aviation system. However, TSA did not conduct the 

necessary analysis of data it collected to assess whether this screening 

change would free up TSOs to focus on screening for high-risk threats, as 

intended. TSA officials acknowledged the importance of evaluating whether 

proposed screening procedures would achieve their intended purpose, but 

cited difficulties in doing so, including time pressures to implement needed 

security measures quickly. Finally, TSA’s documentation on proposed 

modifications to screening procedures was not complete. TSA documented 

the basis—that is, the information, experience, or event that encouraged 

TSA officials to propose the modifications—for 72 of the 92 proposed 

modifications. In addition, TSA documented the reasoning behind its 

decisions for half (26 of 44) of the proposed modifications that were not 

implemented. Without more complete documentation, TSA may not be able 

to justify key modifications to passenger screening procedures to Congress 

and the traveling public. 

TSA monitors TSO compliance with passenger checkpoint screening 

procedures through its performance accountability and standards system 

and through covert testing. Compliance assessments include quarterly 

observations of TSOs’ ability to perform particular screening functions in the 

operating environment, quarterly quizzes to assess TSOs’ knowledge of 

procedures, and an annual knowledge and skills assessment. TSA uses 

covert tests to evaluate, in part, the extent to which TSOs’ noncompliance 

with procedures affects their ability to detect simulated threat items hidden 

in accessible property or concealed on a person. TSA airport officials have

experienced resource challenges in implementing these compliance 

monitoring methods. TSA headquarters officials stated that they are taking 

steps to address these challenges. 

What GAO Recommends

In the March 2007 report that

contained sensitive security

information, GAO recommended,

and the Department of Homeland

Security concurred, that TSA 

develop sound methods to assess

whether proposed screening 

changes would achieve their 

intended purpose and generate 

complete documentation on

proposed screening changes that

are deemed significant. 

www.gao.gov/cgi-bin/getrpt?GAO-07-634.

To view the full product, including the scope 

and methodology, click on the link above. 

For more information, contact Cathleen 

Berrick at (202) 512-3404 or

berrickc@gao.gov. 
Contents 

Letter 1

Results in Brief 4 

Background 8

TSA Considered Risk, Experience, and Customer Concerns when 

Modifying Passenger Screening Procedures, but Could Improve 

Its Evaluation and Documentation of Proposed Procedures 15 

TSA Has Several Methods in Place to Monitor TSO Compliance 

with Passenger Checkpoint Screening SOPs 44 

Conclusions 48

Recommendations for Executive Action 50 

Agency Comments and Our Evaluation 50 

Appendix I Objectives, Scope and Methodology 53 

Appendix II Sources of SOP Changes 58 

Appendix III Comments from the Department of Homeland 

Security 60 

Appendix IV GAO Contact and Staff Acknowledgments 64 

GAO Related Products 65 

Page i GAO-07-634 Aviation Security
Tables 

Table 1: Categories of Proposed and Implemented Passenger 

Checkpoint Screening Changes Considered between April 

2005 and December 2005 14 

Table 2: Factors Considered by TSA When Deciding How to Modify 

Passenger Checkpoint Screening SOPs in Response to the 

Alleged August 2006 Terrorist Plot to Detonate Liquid 

Explosives on U.S.-Bound Aircraft 22 

Table 3: Proposed Procedures Operationally Tested by the 

Explosives Detection Improvement Task Force, October 

2005-January 2006 31 

Table 4: TSA Evaluation of Documentation of Agency Decisions 

Made between August 7 and August 13, 2006, Regarding 

the Alleged Liquid Explosives Terrorist Plot 43 

Table 5: Modules Included in Recertification Knowledge and Skills 

Assessment 46

Figures 

Figure 1: Passenger Checkpoint Screening Functions 9 

Figure 2: TSA Airport Screening Positions 11 

Page ii GAO-07-634 Aviation Security
Abbreviations 

ATSA Aviation and Transportation Security Act 

CAPPS computer-assisted passenger prescreening system

CBP Customs and Border Protection 

COMPEX Compliance Examination 

DHS Department of Homeland Security 

ETD explosive trace detection 

ETP explosives trace portal 

FBI Federal Bureau of Investigation 

FEMA Federal Emergency Management Agency 

FFDO Federal Flight Deck Officer 

FSD Federal Security Director 

HHMD hand-held metal detector

IED improvised explosive device 

PASS Performance Accountability and Standards System 

PMIS Performance Management Information System 

PWD person with disabilities 

SOP standard operating procedure 

SPOT Screening Passengers by Observation Technique

STEA Screener Training Exercises and Assessments 

TIP Threat Image Projection

TSA Transportation Security Administration 

TSO transportation security officer 

USP Unpredictable Screening Process 

WTMD walk-through metal detector 

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 iii GAO-07-634 Aviation Security
United States Government Accountability Office

Washington, DC 20548 

 

April 16, 2007

The Honorable Bennie Thompson 

Chairman, Committee on Homeland Security 

House of Representatives 

The Honorable John Mica 

Ranking Republican Member 

Committee on Transportation and Infrastructure 

House of Representatives 

The alleged August 2006 terrorist plot to detonate liquid explosives 

onboard multiple commercial aircraft bound for the United States from 

the United Kingdom has highlighted the continued importance of securing

the commercial aviation system. The Transportation Security 

Administration (TSA) is responsible for, among other things, securing the 

nation’s commercial aviation system while also facilitating the movement 

of passengers. To protect this system after the September 11, 2001, 

terrorist attacks, TSA implemented a multilayered system of security—the 

most publicly visible layer being the physical screening of passengers and 

their carry-on bags at airport screening checkpoints, which all passengers 

must pass through prior to entering an airport’s sterile area, the area 

within the terminal that provides passengers access to boarding aircraft.1

The passenger checkpoint screening system is composed of three 

elements: (1) the people responsible for conducting the screening of 

airline passengers and their carry-on items—Transportation Security 

Officers (TSO) (formerly known as screeners), (2) the procedures TSOs 

are to follow to conduct screening, and (3) the technology used in the 

screening process. Collectively, these elements help to determine the 

effectiveness and efficiency of passenger checkpoint screening. TSA has 

made efforts to enhance each of the three elements of the passenger 

checkpoint screening system. 

Since its inception, TSA has issued 25 versions of the passenger 

checkpoint screening standard operating procedures (SOP), to include 

 1

In addition to passenger checkpoint screening, TSA’s layers of aviation security include, 

among other things, the screening of all checked baggage for explosives and the 

deployment of Federal Air Marshals on designated high-risk flights. 

Page 1 GAO-07-634 Aviation Security
new screening procedures as well as changes to existing screening 

procedures. Several of these revisions have been criticized and scrutinized 

by the traveling public and Congress. For example, in September 2004, 

TSA modified its passenger screening procedures in response to the 

August 2004 midair explosions of two Russian airliners, believed to have 

been caused by Chechen women who concealed explosive devices under 

their clothing. Specifically, the revision entailed a more invasive technique 

for patting down the torso area of passengers. According to TSA officials, 

in response to complaints raised by airline passengers and TSA’s review of 

additional threat information, TSA further modified the pat-down 

procedure in December 2004 to entail a more targeted, less intrusive patdown procedure. In December 2005, TSA allowed passengers to carry 

small scissors and small tools onto aircraft, resulting in concern by some 

industry representatives that allowing sharp objects onto planes would put 

flight crew at risk of attack.2

 This procedural change also resulted in the 

TSA Assistant Secretary being asked to testify before Congress on the 

agency’s rationale for allowing passengers to carry small scissors and 

small tools onto planes and a legislative mandate for us to assess the 

impact of the prohibited items list change on public safety and screening 

operations.3

In light of the potential impact of changes to passenger checkpoint 

screening procedures, you asked that we assess TSA’s process for 

determining whether and how screening procedures should be modified, 

to include the creation of new screening procedures and changes to 

existing screening procedures. Specifically, this report addresses the 

following questions: (1) How and on what basis did TSA modify passenger

screening procedures and what factors guided the decisions to do so? 

(2) How does TSA determine whether TSOs are complying with the 

standard procedures for screening passengers and their carry-on items? 

In March 2007, we issued a report that contained sensitive security 

information regarding TSA’s passenger checkpoint screening procedures, 

including the factors TSA considered when modifying passenger screening 

procedures and TSA’s efforts to monitor TSO compliance with standard 

 2

Specifically, TSA modified the list of items prohibited and permitted on aircraft by

allowing metal scissors with pointed tips and a cutting edge of 4 inches or less, as 

measured from the fulcrum, and small tools of 7 inches or less, including screwdrivers, 

wrenches, and pliers, to pass through the passenger screening checkpoint. See 70 Fed. 

Reg. 72,930 (Dec. 8, 2005). 

3

We plan to issue a report on the impact of the prohibited items list changes on public 

safety and screening operations later this year. 

Page 2 GAO-07-634 Aviation Security
passenger screening procedures. This report provides the results of our 

March 2007 report with sensitive security information removed. 

To obtain information on the process used to modify passenger 

checkpoint screening procedures, we reviewed and analyzed available 

TSA documentation on proposed procedure modifications that were 

considered between April 2005 and December 2005, as well as threat 

assessments and operational studies that supported SOP modifications.4

We also reviewed and analyzed similar documentation for proposed 

modifications considered between August 2006 and November 2006 in 

response to the alleged terrorist plot to detonate liquid explosives onboard

multiple aircraft en route from the United Kingdom to the United States. 

We included modifications to passenger checkpoint screening procedures

related to this particular event because they provided the most recent 

information available of TSA’s approach to modifying screening 

procedures in response to an immediate perceived threat to civil aviation.

To assess TSO compliance with standard operating procedures, our work 

also involved a review of available documentation, including guidance, 

checklists, and other evaluation tools used by TSA. In addition, we met 

with TSA headquarters officials who were involved in the process of 

determining whether proposed changes to passenger checkpoint screening 

procedures should be implemented, and who were responsible for 

overseeing efforts to monitor TSO compliance with screening procedures.

We also visited or conducted phone interviews with staff at 25 airports, 

which we selected based on variation in size, geographic location, and 

level of performance on compliance-related assessments. At each airport, 

we interviewed Federal Security Directors (FSD),5

 members of their 

management teams, and TSOs with passenger screening responsibilities. 

Information from these interviews cannot be generalized to all airports 

nationwide. Two of the airports we visited were also participants in TSA’s 

 4

We began our review period in April 2005 to coincide with TSA’s consideration of

proposed SOP modifications related to the second major revision of the passenger 

checkpoint screening SOP since TSA’s inception.

5

TSA security activities at airports are overseen by FSDs. Each FSD is responsible for

overseeing security activities, including passenger screening, at one or more commercial 

airports. We visited or conducted phone interviews with officials at 25 airports. However,

we met with only 24 FSDs, as 1 FSD was responsible for 2 of the airports we visited. 

Page 3 GAO-07-634 Aviation Security
Screening Partnership Program.6

 We also met with officials from the 

Department of Homeland Security (DHS) Science and Technology 

Directorate as well as the Federal Bureau of Investigation (FBI) to discuss 

the methodology and results of their liquid explosives tests, which were 

used to support TSA’s decisions to modify the SOP in September 2006. We 

also interviewed five experts in the field of aviation security to obtain their 

perspectives on TSA’s approach for deciding whether to implement 

proposed checkpoint screening procedures.7

 We compared TSA’s 

approach for implementing and revising passenger checkpoint screening 

procedures, and for monitoring TSO compliance, with the Comptroller 

General’s standards for internal control in the federal government8

 and 

with risk management guidance. We assessed the reliability of the data we 

acquired from TSA regarding TSO compliance and found the data to be 

sufficiently reliable for our purposes. 

We conducted our work from March 2005 through January 2007 in 

accordance with generally accepted government auditing standards. More 

details about the scope and methodology of our work are presented in 

appendix I. 

During our 9-month review period, proposed modifications to passenger 

checkpoint screening procedures were made in various ways and for a 

variety of reasons, and while a majority of the proposed modifications— 

48 of 92—were ultimately implemented at airports, TSA’s methods for 

evaluating and documenting them could be improved. Some SOP 

Results in Brief 

 6

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

(2001), established TSA and assigned TSA with the responsibility of building a federal 

workforce to conduct screening of airline passengers and their checked baggage. See 

49 U.S.C. §§ 114(a), 44901(a). ATSA also required that TSA allow commercial airports to

apply to TSA to transition from a federal to a private screener workforce. See 49 U.S.C 

§ 44920. To support this effort, TSA created the Screening Partnership Program to allow all 

commercial airports an opportunity to apply to TSA for permission to use qualified private 

screening contractors and private screeners. There are currently 6 airports participating in 

the Screening Partnership Program, including Jackson Hole, Kansas City International, 

Greater Rochester International, San Francisco International, Sioux Falls Regional, and 

Tupelo Regional. 

7

We used the following criteria to identify aviation security experts: present and past

employment in aviation security, depth of experience in aviation security, and recognition 

in the aviation industry. 

8

GAO, Internal Control: Standards for Internal Control in the Federal Government, 

GAO/AIMD-00-21.3.1 (Washington, D.C.: August 2001). 

Page 4 GAO-07-634 Aviation Security
modifications were proposed based on the professional judgment of TSA 

senior-level officials and program-level staff at headquarters and at 

airports nationwide, while other modifications were proposed by members 

of a TSA task force charged with enhancing TSA’s ability to detect 

improvised explosive devices at checkpoints. TSA officials proposed SOP 

modifications based on risk information (threat and vulnerability 

information), daily experiences of staff working at airports, and 

complaints and concerns raised by the traveling public. In addition to 

these factors, TSA senior leadership made efforts to balance the impact 

that proposed SOP modifications—such as the changes to the liquids, gels,

and aerosols screening procedures—would have on security, efficiency, 

and customer service when deciding whether proposed SOP modifications 

should be implemented. In some cases, TSA first tested proposed 

modifications to screening procedures at selected airports to help 

determine whether the changes would achieve their intended purpose, 

such as to enhance detection of prohibited items or to free up TSO 

resources to perform screening activities focused on threats considered to 

pose a high risk, such as explosives. However, TSA’s data collection and 

analyses could be improved to help TSA determine whether proposed 

procedures that are operationally tested would achieve their intended 

purpose. Specifically, for the seven tests of proposed screening 

procedures TSA conducted during our review period, although TSA 

collected some data on the efficiency of and customer response to the 

procedures at selected airports, the agency generally did not collect the 

type of data or conduct the necessary analysis that would yield 

information on whether proposed procedures would achieve their 

intended purpose. TSA officials acknowledged that they could have made 

some improvements in the various analyses they conducted related to the 

decision to allow small scissors and tools onboard aircraft, but cited 

several difficulties in doing so. Nevertheless, until TSA takes steps to 

improve its ability to evaluate the potential impact of screening changes 

on security and TSO resource availability, it may be difficult for TSA to 

determine how best to allocate limited TSO resources, help ensure the 

screeners’ ability to detect explosives and other high-threat objects, and 

evaluate whether proposed modifications to screening procedures would 

have the intended effect. Finally, TSA’s documentation on proposed 

modifications to screening procedures was not always complete. TSA 

documented the basis—that is, the information, experience, or event that

encouraged TSA officials to propose the modifications—for 72 of the 

92 proposed modifications. In addition, TSA only documented the 

reasoning behind its decisions for about half (26 of 44) of the proposed 

modifications that were not implemented. Our standards for governmental 

internal controls and associated guidance suggest that agencies should 

Page 5 GAO-07-634 Aviation Security
document key decisions in a way that is complete and accurate. Without 

such information, TSA cannot always justify significant SOP modifications 

to Congress and the traveling public. TSA officials acknowledged that it is 

beneficial to maintain documentation on the reasoning behind decisions to

implement or reject proposed SOP modifications deemed significant, 

particularly given the organizational restructuring and staff turnover 

within TSA. 

TSA monitors TSO compliance with passenger checkpoint screening SOPs 

through its performance accountability and standards system and through 

local and national covert testing.9

 According to TSA officials, the agency

developed the performance accountability and standards system in 

response to our 2003 report that recommended that TSA establish a 

performance management system that makes meaningful distinctions in 

employee performance,10 and in response to input from TSA airport staff 

on how to improve passenger and checked baggage screening measures. 

This system is used by TSA to measure TSO compliance with passenger 

checkpoint screening procedures. Of the 24 FSDs we interviewed about 

compliance assessments, 9 cited difficulties in implementing the 

performance accountability and standards system because of a lack of 

available staff to conduct observations and administer SOP quizzes. When 

asked whether they planned to address FSDs’ concerns regarding a lack of 

available staff to evaluate TSO compliance with SOPs, TSA headquarters 

officials said that they have automated many of the data entry functions of 

the performance accountability and standards system to relieve the field of 

the burden of manually entering this information into the online system. 

Furthermore, the TSA Assistant Secretary stated that FSDs were given the 

option of delaying implementation of the performance accountability and 

standards system if they were experiencing resource challenges. In 

addition to implementing the performance accountability and standards 

system, TSA conducts local and national covert tests to evaluate, in part, 

the extent to which TSOs’ noncompliance with the SOPs affects their 

ability to detect simulated threat items hidden in accessible property or 

 9

Covert testing involves TSA headquarters officials (national testing) or TSA field staff and 

other federal employees (local testing) attempting to carry simulated threat objects 

through the checkpoint without the objects being detected by TSOs. The results of the 

national covert tests are classified and therefore are not included in this report.)

10GAO, Transportation Security Administration: Actions and Plans to Build a Results 

Oriented Culture, GAO-03-190 (Washington, D.C.: January 2003). 

Page 6 GAO-07-634 Aviation Security
concealed on a person.11 Even though all 24 FSDs said that they have 

conducted local covert tests, 10 of these FSDs said that lack of available 

staff made it difficult to conduct these tests. TSA officials told us that they 

are considering resource alternatives for implementing these tests, but did 

not provide us with specific details of these plans. Based on the results of 

national covert tests conducted between September 2005 and July 2006, 

which showed that some TSOs did not identify threat objects, in part 

because they did not comply with SOPs, TSA’s Office of Inspection 

recommended, among other things, that the Office of Security Operations 

ensure that TSOs adhere to the current passenger checkpoint screening

SOPs. However, until the resource limitations that have restricted TSA’s 

use of its compliance monitoring tools have been fully addressed, TSA 

may not have assurance that TSOs are screening passengers according to 

standard procedures. 

To help improve TSA’s ability to evaluate proposed SOP modifications and 

to justify its decisions regarding whether proposed SOP modifications 

should be implemented, in the March 2007 report that contained sensitive 

security information, we recommended that the Secretary of the 

Department of Homeland Security direct the Assistant Secretary of 

Homeland Security for TSA to (1) develop sound evaluation methods, 

when possible, that can help TSA determine whether proposed procedures 

that are operationally tested would achieve their intended purpose, and 

(2) generate and maintain complete documentation of proposed 

modifications deemed significant by TSA. DHS generally concurred with 

our findings and recommendations and outlined actions TSA plans to take

to implement the recommendations. For example, TSA intends to improve 

its methods for evaluating proposed SOP modifications, which may entail

randomly selecting the airports that will participate in a study to better 

isolate the impact of proposed SOP modifications on passenger screening. 

DHS also stated that TSA is in the process of developing protocols that 

will require documentation of the source and intent of proposed SOP 

modifications, as well as documentation of TSA officials’ reasoning for 

implementing or rejecting proposed modifications. The full text of DHS’s 

comments is included in appendix III. 

 11The results of local covert testing are sensitive security information and, therefore, are

not included in this report. 

Page 7 GAO-07-634 Aviation Security
Passenger screening is a process by which personnel authorized by TSA 

inspect individuals and property to deter and prevent the carriage of any

unauthorized explosive, incendiary, weapon, or other dangerous item 

onboard an aircraft or into a sterile area.12 Passenger screening personnel 

must inspect individuals for prohibited items at designated screening 

locations.13 As shown in figure 1, the four passenger screening functions 

are 

Background 

Passenger Checkpoint 

Screening System 

• X-ray screening of property, 

• walk-through metal detector screening of individuals, 

• hand-wand or pat-down screening of individuals, and 

• physical search of property and trace detection for explosives.

Typically, passengers are only subjected to X-ray screening of their carryon items and screening by the walk-through metal detector. Passengers 

whose carry-on baggage alarms the X-ray machine, who alarm the walkthrough metal detector, or who are designated as selectees—that is, 

passengers selected by the Computer-Assisted Passenger Prescreening 

System (CAPPS)14 or other TSA-approved processes to receive additional 

screening—are screened by hand-wand or pat-down and have their carryon items screened for explosives traces or physically searched. 

 12Sterile areas are located within the terminal where passengers are provided access to 

boarding aircraft. Access to these areas is controlled by Transportation Security Officers

(or by nonfederal screeners at airports participating in the Screener Partnership Program)

at checkpoints where they conduct physical screening of individuals and their carry-on 

baggage for weapons, explosives, and other prohibited items. 

13Transportation Security Officers must deny passage beyond the screening location to any 

individual or property that has not been screened or inspected in accordance with 

passenger screening standard operating procedures. If an individual refuses to permit 

inspection of any item, that item must not be allowed into the sterile area or onboard an

aircraft. 

14CAPPS is a computer-assisted system that, based on information obtained from airline 

reservation systems, identifies passengers that may pose a high risk to aviation security. 

These high-risk passengers and their carry-on baggage are subject to additional and more 

thorough screening. 

Page 8 GAO-07-634 Aviation Security
Figure 1: Passenger Checkpoint Screening Functions 

Behavior Detection Officer (BDO)a

Manual or ETD searchesc

Video surveillance

Source: GAO and Nova Development Corporation.

Passenger screening functions

X-ray

X-ray

X-ray screening

Physical barriers

(walls/partitions)

Walk-though

metal detector screening

Hand-wand or pat-downb

Note: Explosive trace detection (ETD) works by detecting vapors and residues of explosives. Human 

operators collect samples by rubbing swabs along the interior and exterior of an object that TSOs 

determine to be suspicious, and place the swabs in the ETD machine, which then chemically 

analyzes the swab to identify any traces of explosive materials. 

Bomb Appraisal Officers (BAO) are available to respond to unresolved alarms at the checkpoint that 

involve possible explosive devices. The BAO may contact appropriate law enforcement or bomb 

squad officials if review indicates possible or imminent danger, in which case the BAO ensures that

the security checkpoint is cleared. The BAO approves reopening of security lane(s) if no threat is

posed. 

a

BDOs are TSOs specially trained to detect suspicious behavior in individuals approaching the 

checkpoint. Should the BDO observe such behavior, he or she may refer the individual for additional 

screening or to a law enforcement officer. 

b

The hand-wand or pat-down is conducted if a passenger is identified or randomly selected for 

additional screening because he or she met certain criteria or alarmed the walk-through metal 

detector. 

c

Manual or ETD searches of accessible property occur if the passenger is identified or randomly 

selected for additional screening or if the screener identified a potential prohibited item on X-ray. 

Page 9 GAO-07-634 Aviation Security
The passenger checkpoint screening system is composed of three 

elements: the people responsible for conducting the screening of airline 

passengers and their carry-on items—TSOs, the technology used during 

the screening process, and the procedures TSOs are to follow to conduct 

screening. Collectively, these elements help to determine the effectiveness 

and efficiency of passenger checkpoint screening. 

TSOs screen all passengers and their carry-on baggage prior to allowing 

passengers access to their departure gates. There are several positions 

within TSA that perform and directly supervise passenger screening 

functions. Figure 2 provides a description of these positions. 

Transportation Security 

Officers 

Page 10 GAO-07-634 Aviation Security
Figure 2: TSA Airport Screening Positions 

Screening

Manager

1,041 positionsa

Supervisory 

Transportation

Security

Officer

4,308 positionsa

Transportation

Security

Officer

35,414 positionsa

Manages screening checkpoints that are central to TSA objectives that serve to protect the traveling public by preventing 

any deadly or dangerous objects from being transported onto an aircraft.

Recognizes and recommends correction of improper use or application of the equipment, provides guidance to 

subordinates, and answers routine questions presented by subordinates.

Manages and supports the collection of various performance metrics in an effort to identify areas in need of process

improvement and systemic or individual weaknesses, vulnerabilities, or inefficiencies in the screening process.

Coordinates national and local crisis management and incident response protocols.

Recognizes and understands the customer service needs of the traveling public and balances these needs with 

safety and security in mind. 

Works cooperatively with airport stakeholders in furtherance of the TSA mission.

Monitors individual performance and provides frequent communication in order to promote TSO 

development.

Oversees the screening checkpoint on a daily basis, scheduling an adequate number of screeners to 

provide efficient screening of all persons, baggage, and cargo.

Conducts screening of passengers, baggage, and cargo.

Works closely with screeners, managers, airport security staff, and law enforcement personnel at 

checkpoints.

Directs work of employees, assigning tasks and monitoring and evaluating performance.

Enforces TSA SOPs to prevent security breaches. 

Participates in information briefings concerning security-sensitive or classified information.

Maintains communication with management regarding issues that might reveal a security 

weakness.

Oversees the screening checkpoint on a daily basis, scheduling an adequate number of 

screeners to provide efficient screening of all persons, baggage, and cargo. 

Distributes and balances workload and tasks among employees, making 

adjustments as necessary.

Conducts screening of passengers, baggage, and cargo, monitoring the flow of 

passengers through the screening checkpoint.

Enforces TSA SOPs to prevent deadly or dangerous objects from being 

transported onto an aircraft.

Monitors and reports on the status and progress of work, serving as a team 

builder among screeners.

Resolves informal complaints and serves as liaison between supervisor 

and incumbent screeners for formal complaints.

Performs preboard screening of persons and their carry-on checked 

baggage.

Implements security-screening procedures that are central to 

TSA objectives and will serve to protect the traveling public by 

preventing any deadly or dangerous objects from being 

transported onto the aircraft.

Assists in monitoring the flow of passengers through the 

screening checkpoint.

Positions Major functions

Source: GAO analysis of TSA data.

Lead 

Transportation

Security

Officer

5,278 positionsa

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

·

a

Number of annualized TSA screening positions for fiscal year 2006. These positions do not include 

private screener positions at the six airports that participated in the Screening Partnership Program 

during fiscal year 2006. 

Page 11 GAO-07-634 Aviation Security
In May 2005, we reported on TSA’s efforts to train TSOs and to measure 

and enhance TSO performance.15 We found that TSA had initiated a 

number of actions designed to enhance passenger TSO, checked baggage 

TSO, and supervisory TSO training. However, at some airports TSOs 

encountered difficulty accessing and completing recurrent (refresher) 

training because of technological and staffing constraints. We also found

that TSA lacked adequate internal controls to provide reasonable 

assurance that TSOs were receiving legislatively mandated basic and 

remedial training, and to monitor the status of its recurrent training 

program. Further, we reported that TSA had implemented and 

strengthened efforts to collect TSO performance data as part of its overall

effort to enhance TSO performance. We recommended that TSA develop a 

plan for completing the deployment of high-speed Internet/intranet 

connectivity to all TSA airport training facilities, and establish appropriate 

responsibilities and other internal controls for monitoring and 

documenting TSO compliance with training requirements. DHS generally

concurred with our recommendations and stated that TSA has taken steps 

to implement them. 

There are typically four types of technology used to screen airline 

passengers and their carry-on baggage at the checkpoint: 

Screening Technology

• walk-through metal detectors, 

• X-ray machines, 

• hand-held metal detectors, and 

• explosive trace detection (ETD) equipment. 

The President’s fiscal year 2007 budget request noted that emerging 

checkpoint technology will enhance the detection of prohibited items, 

especially firearms and explosives, on passengers. As of December 2006,

TSA plans to conduct operational tests of three types of passenger 

screening technologies within the next year. TSA has conducted other 

tests in the past; for example, during fiscal year 2005, TSA operationally 

tested document scanners, which use explosive trace detection technology 

to detect explosives residue on passengers’ boarding passes or 

identification cards. TSA decided not to expand the use of the document 

scanner, in part because of the extent to which explosives traces had to be 

sampled manually. TSA also plans to begin operational tests of technology 

 15GAO, Aviation Security: Screener Training and Performance Measurement 

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

Page 12 GAO-07-634 Aviation Security
that would screen bottles for liquid explosives. We are currently evaluating

the Department of Homeland Security’s and TSA’s progress in planning 

for, managing, and deploying research and development programs in 

support of airport checkpoint screening operations. We expect to report 

our results in August 2007. 

TSA has developed checkpoint screening standard operating procedures, 

which are the focus of this report, that establish the process and standards 

by which TSOs are to screen passengers and their carry-on items at 

screening checkpoints.16 Between April 2005 and December 2005, based on

available documentation, TSA deliberated 189 proposed changes to 

passenger checkpoint screening SOPs, 92 of which were intended to 

modify the way in which passengers and their carry-on items are 

screened.17 TSA issued six versions of the passenger checkpoint screening 

SOPs during this period.18

Standard Operating Procedures 

TSA modified passenger checkpoint screening SOPs to enhance the 

traveling public’s perception of the screening process, improve the 

efficiency of the screening process, and enhance the detection of 

prohibited items and suspicious persons. As shown in table 1, 48 of the 

92 proposed modifications to passenger checkpoint screening SOPs were 

implemented, and the types of modifications made or proposed generally 

 16Private screeners conduct passenger and checked baggage screening at six airports as 

part of TSA’s Screening Partnership Program. TSA requires that private screeners screen

passengers using the same standard operating procedures as TSOs. 

17Between April 2005 and December 2005, TSA considered a total of 189 proposed 

modifications to passenger checkpoint screening SOPs. However, 97 of the proposed

modifications were not intended to alter the way in which passengers and their carry-on 

items are screened; rather, these modifications were generally intended to correct, edit, or

clarify SOP language. For example, TSA modified SOP language to ensure that TSA field 

staff were aware that tribal law enforcement officers should be granted the same screening 

exemptions as other law enforcement officers. TSA also amended the SOP to help ensure 

the occupational safety of TSOs. For example, TSA headquarters officials proposed that

procedures for reporting potential radiation hazards regarding X-ray equipment be

incorporated into the SOP. The remaining 92 proposed SOP modifications were intended to 

alter the way in which passengers and their carry-on items were screened, and 48 of those 

proposed modifications were subsequently implemented. 

18TSA issued six revised versions of the passenger checkpoint screening SOP during the 

9-month period under review: April 7, 2005; July 7, 2005; August 26, 2005; September 12, 

2005; October 25, 2005; and December 7, 2005. However, we did not include the April 2005 

revised SOP in our review since the changes incorporated in that revision were deliberated

by TSA officials outside of our 9-month period of review. 

Page 13 GAO-07-634 Aviation Security
fell into one of three categories—customer satisfaction, screening 

efficiency, and security.

Table 1: Categories of Proposed and Implemented Passenger Checkpoint

Screening Changes Considered between April 2005 and December 2005 

Category of 

proposed changes Description of category 

Proposed

SOP changes

Implemented

SOP changes

Customer satisfaction Changes that will improve the 

traveling public’s perception 

of the screening process or 

reduce or exempt categories

of authorized individuals from

certain aspects of the 

screening process. 

42 22

Screening efficiency Changes that will improve 

screening flow, clarify 

screener duties, update 

equipment procedures, or 

enhance the working 

environment of screening 

locations. 

31 17

Security Changes that will improve 

TSA’s ability to detect 

prohibited items and 

suspicious persons. 

19 9

Total 92 48

Source: GAO analysis of TSA data. 

Page 14 GAO-07-634 Aviation Security
TSA used various processes between April 2005 and December 2005 to

modify passenger checkpoint screening SOPs, and a variety of factors 

guided TSA’s decisions to modify SOPs. TSA’s processes for modifying 

SOPs generally involved TSA staff recommending proposed modifications, 

reviewing and commenting on proposed modifications, and TSA senior 

leadership making final decisions as to whether proposed modifications 

should be implemented. During our 9-month review period, TSA officials 

considered 92 proposed modifications to the way in which passengers and 

their carry-on items were screened, and 48 were implemented.19 TSA 

officials proposed SOP modifications based on risk factors (threat and 

vulnerability information), day-to-day experiences of airport staff, and 

concerns and complaints raised by passengers. TSA then made efforts to 

balance security, efficiency, and customer service when deciding which 

proposed SOP modifications to implement. Consistent with our prior work 

that has shown the importance of data collection and analyses to support 

agency decision making, TSA conducted data collection and analysis for 

certain proposed SOP modifications that were tested before they were 

implemented at all airports. Nevertheless, we found that TSA could 

improve its data collection and analysis to assist the agency in determining 

whether the proposed procedures would enhance detection or free up 

TSO resources, when intended. In addition, TSA did not maintain complete

documentation of proposed SOP modifications; therefore, we could not 

fully assess the basis for proposed SOP modifications or the reasons why 

certain proposed modifications were not implemented. TSA officials 

acknowledged that it is beneficial to maintain documentation on the 

reasoning behind decisions to implement or reject SOP modifications 

deemed significant. 

Proposed SOP modifications were submitted and reviewed under two 

processes during our 9-month review period, and for each process, TSA 

senior leadership made the final decision as to whether the proposed 

modifications would be implemented. One of the processes TSA used to 

modify passenger checkpoint screening SOPs involved TSA field staff or 

headquarters officials, and, to a lesser extent, TSA senior leadership, 

suggesting ways in which passenger checkpoint screening SOPs could be 

modified. These suggestions were submitted through various mechanisms, 

TSA Considered Risk, 

Experience, and 

Customer Concerns 

when Modifying 

Passenger Screening 

Procedures, but Could 

Improve Its 

Evaluation and 

Documentation of 

Proposed Procedures 

TSA’s Processes for 

Modifying SOPs Were 

Driven by Input from TSA 

Field and Headquarters 

Staff 

 19Of the 48 proposed modifications that were implemented, TSA made the decision to 

implement 16 of these modifications following our 9-month review period. However,

because much of TSA’s deliberation of these 16 procedures occurred during our review 

period, we included these procedures among those that were implemented. 

Page 15 GAO-07-634 Aviation Security
including electronic mail and an SOP panel review conducted by TSA 

airport personnel. (These methods are described in more detail in app. II.) 

Eighty-two of the 92 proposed modifications were considered under this 

process. 

If TSA officials determined, based on their professional judgment, that the 

recommended SOP modifications—whether from headquarters or the 

field—merited further consideration, or if a specific modification was 

proposed by TSA senior leadership, the following chain of events 

occurred: 

• First, the procedures branch of the Office of Security Operations 

drafted SOP language for each of the proposed modifications.20

• Second, the draft language for each proposed modification was 

disseminated to representatives of various TSA divisions for review, 

and the language was revised as needed. 

• Third, TSA officials tested proposed modifications in the airport 

operating environment if they found it necessary to: 

• assess the security impact of the proposed modification, 

• evaluate the impact of the modification on the amount of time 

taken for passengers to clear the checkpoint, 

• measure the impact of the proposed modification on passengers 

and industry partners, or 

• determine training needs created by the proposed modification. 

• Fourth, the revised SOP language for proposed modifications was 

sent to the heads of several TSA divisions for comment. 

• Fifth, considering the comments of the TSA division heads, the head

of the Office of Security Operations or other TSA senior leadership 

made the final decision as to whether proposed modifications 

would be implemented. 

Another process for modifying passenger checkpoint screening SOPs 

during our 9-month review period was carried out by TSA’s Explosives 

Detection Improvement Task Force. The task force was established in 

October 2005 by the TSA Assistant Secretary to respond to the threat of 

improvised explosive devices (IED) being carried through the checkpoint. 

The goal of the task force was to apply a risk-based approach to screening 

passengers and their baggage in order to enhance TSA’s ability to detect 

 20The Office of Security Operations is the TSA division responsible for overseeing the 

implementation of passenger and property screening at airport checkpoints. 

Page 16 GAO-07-634 Aviation Security
IEDs.21 The task force developed 13 of the 92 proposed SOP modifications 

that were considered by TSA between April 2005 and December 2005.22

The task force solicited and incorporated feedback from representatives 

of various TSA divisions on these proposed modifications and presented 

them to TSA senior leadership for review and approval. TSA senior 

leadership decided that 8 of the 13 proposed modifications should be 

operationally tested—that is, temporarily implemented in the airport 

environment for the purposes of data collection and evaluation—to better 

inform decisions regarding whether the proposed modifications should be 

implemented. Following the testing of these proposed modifications in the 

airport environment, TSA senior leadership decided to implement 7 of the 

8 operationally tested changes.23 (The task force’s approach to testing 

these procedures is discussed in more detail below.) Following our 

9-month period of review, the changes that TSA made to its passenger 

checkpoint screening SOPs in response to the alleged August 2006 liquid 

explosives terror plot were decided upon by DHS and TSA senior 

leadership, with some input from TSA field staff, aviation industry 

representatives, and officials from other federal agencies. 

Risk Factors, Day-to-Day 

Experiences, and 

Customer Concerns Were 

the Basis for Proposed 

SOP Modifications 

Based on available documentation,24 risk factors (i.e., threats to

commercial aviation and vulnerability to those threats), day-to-day 

experiences of airport staff, and complaints and concerns raised by 

passengers were the basis for TSA staff and officials proposing 

modifications to passenger checkpoint screening SOPs. 

Fourteen of the 92 procedure modifications recommended by TSA staff 

and officials were based on reported or perceived threats to commercial 

aviation, and existing vulnerabilities to those threats. For example, the 

 21In order to achieve its goal of improving IED detection, in addition to modifying 

passenger checkpoint screening SOPs, the task force established several initiatives, 

including enhanced bomb detection training for TSOs and increased use of explosives 

detection canine teams. 

22Three of the 92 proposed SOP modifications were considered by TSA under both 

processes. 

23The number of airports at which any one proposed change was pilot tested ranged from

3 to 14, and the duration of the pilot testing ranged from 5 days to several weeks. 

24The number of proposed SOP modifications that fall under the various “basis” categories 

(e.g., threat and vulnerability information) does not total 92 because documentation was 

not available for all proposed modifications and some of the proposed modifications had 

more than one basis.

Page 17 GAO-07-634 Aviation Security
Explosives Detection Improvement Task Force proposed SOP 

modifications based on threat reports developed by TSA’s Intelligence and 

Analysis division. Specifically, in an August 2005 civil aviation threat 

assessment, the division reported that terrorists are likely to seek novel 

ways to evade U.S. airport security screening.25 Subsequently, the task 

force proposed that the pat-down procedure performed on passengers 

selected for additional screening be revised to include not only the torso 

area, which is what the previous pat-down procedure entailed, but 

additional areas of the body such as the legs.26 The August 2005 threat 

assessment also stated that terrorists may attempt to carry separate 

components of an IED through the checkpoint, then assemble the 

components while onboard the aircraft. To address this threat, the task 

force proposed a new procedure to enhance TSOs’ ability to search for 

components of improvised explosive devices. According to TSA officials, 

threat reports have also indicated that terrorists rely on the routine nature

of security measures in order to plan their attacks. To address this threat, 

the task force proposed a procedure that incorporated unpredictability 

into the screening process by requiring designated TSOs to randomly 

select passengers to receive additional search procedures. Following our 

9-month review period, TSA continued to use threat information as the 

basis for proposed modifications to passenger checkpoint screening SOPs. 

In August 2006, TSA proposed modifications to passenger checkpoint 

screening SOPs after receiving threat information regarding an alleged 

terrorist plot to detonate liquid explosives onboard multiple aircraft en 

route from the United Kingdom to the United States. Regarding 

vulnerabilities to reported threats, based on the results of TSA’s own 

covert tests (undercover, unannounced tests), TSA’s Office of Inspection 

 25We did not assess the quality of the intelligence information used by TSA’s Office of 

Intelligence and Analysis to generate its civil aviation threat assessments. 

26The pat-down procedure is performed for three purposes: (1) as a substitute for walkthrough metal detector screening, (2) to resolve walk-through metal detector alarms, and

(3) as a standard procedure for screening passengers selected for additional screening. The

details of the pat-down procedures are sensitive security information and are not discussed 

in this report. 

Page 18 GAO-07-634 Aviation Security
recommended27 SOP modifications to enhance the detection of explosives 

at the passenger screening checkpoint.28 

TSA officials also proposed modifications to passenger checkpoint 

screening SOPs based on their professional judgment regarding perceived 

threats to aviation security. For example, an FSD recommended changes 

to the screening of funeral urns based on a perceived threat. In some 

cases, proposed SOP modifications appeared to reflect threat information 

analyzed by TSA officials. For example, TSOs are provided with Threat in 

the Spotlight, a weekly report that identifies new threats to commercial 

aviation, examples of innovative ways in which passengers may conceal

prohibited items, and pictures of items that may not appear to be 

prohibited items but actually are. TSOs are also provided relevant threat 

information during briefings that take place before and after their shifts. 

In addition, FSDs are provided classified intelligence summaries on a daily 

and weekly basis, as well as monthly reports of suspicious incidents that 

occurred at airports nationwide. TSA’s consideration of threat and 

vulnerability—through analysis of current documentation and by 

exercising professional judgment—is consistent with a risk-based 

decision-making approach.29 As we have reported previously, and DHS and 

TSA have advocated, a risk-based approach, as applied in the homeland 

security context, can help to more effectively and efficiently prepare 

defenses against acts of terrorism and other threats. 

TSA headquarters and field staff also based proposed SOP modifications—

specifically, 36 of the 92 proposed modifications—on experience in the 

airport environment. For example, TSA headquarters officials conduct 

reviews at airports to identify best practices and deficiencies in the 

checkpoint screening process. During one of these reviews, headquarters 

officials observed that TSOs were not fully complying with the pat-down 

procedure. After discussions with TSOs, TSA headquarters officials 

 27The recommendations made by the Office of Inspection are sensitive security information 

or classified information. Therefore, they are not discussed in this report. 

28The DHS Office of Inspector General conducts similar covert tests, and historically has 

recommended changes to the passenger checkpoint screening SOP as a result of these 

tests. However, the Office of Inspector General did not make any recommendations that

resulted in procedural changes between April 2005 and December 2005. 

29A risk-based approach generally involves consideration of the following when making

decisions: threat—capability and intent of terrorists to carry out an attack, vulnerability—

weakness that may be exploited by identified threats, and criticality or consequence—the

impact of an attack if it were to be carried out. 

Page 19 GAO-07-634 Aviation Security
determined that the way in which TSOs were conducting the procedure 

was more effective. In addition, TSA senior leadership, after learning that

small airports had staffing challenges that precluded them from ensuring 

that passengers are patted down by TSOs of the same gender, proposed 

that opposite-gender pat-down screening be allowed at small airports. 

Passenger complaints and concerns shared with TSA also served as a basis 

for proposed modifications during our 9-month review period. Specifically, 

of the 92 proposed SOP modifications considered during this period, TSA 

staff and officials recommended 29 modifications based on complaints and 

concerns raised by passengers. For example, TSA headquarters staff 

recommended allowing passengers to hold their hair while being screened 

by the Explosives Trace Portal,30 after receiving complaints from 

passengers about eye injuries from hair blowing in their eyes and hair 

being caught in the doors of the portal. 

TSA Balanced Security, 

Efficiency, and Customer 

Service when Deciding 

whether to Implement 

Proposed SOP 

Modifications 

When deciding whether to implement proposed SOP modifications, TSA 

officials also made efforts to balance the impact of proposed modifications 

on security, efficiency,

31 and customer service. TSA’s consideration of 

these factors reflects the agency’s mission to protect transportation 

systems while also ensuring the free movement of people and commerce. 

As previously discussed, TSA sought to improve the security of the 

commercial aviation system by modifying the SOP for conducting the 

pat-down search. (TSA identified the modified pat-down procedure as the 

“bulk-item” pat-down.) When deciding whether to implement the proposed 

modification, TSA officials considered not only the impact that the bulkitem pat-down procedure would have on security, but also the impact that 

the procedure would have on screening efficiency and customer service. 

For example, TSA officials determined that the bulk-item pat-down 

procedure would not significantly affect efficiency because it would only 

add a few seconds to the screening process. Following our 9-month review 

period, TSA continued to make efforts to balance security, efficiency, and 

customer service when deciding whether to implement proposed SOP 

 30Explosives Trace Portal screening entails a passenger stepping into the portal, after which 

puffs of air are emitted onto the passenger. The portal then draws in any residue that was 

loosened as a result of the puffs of air, and analyzes the residue to determine if there are

explosive traces. 

31TSA defines SOP modifications related to efficiency as changes that will improve

screening flow, clarify TSO duties, update equipment procedures, or enhance the working

environment of screening locations. 

Page 20 GAO-07-634 Aviation Security
modifications, as illustrated by TSA senior leadership’s deliberation on 

proposed SOP modifications in response to the alleged August 2006 liquid 

explosives terrorist plot. TSA modified the passenger checkpoint 

screening SOP four times between August 2006 and November 2006 in an

effort to defend against the threat of terrorists’ use of liquid explosives 

onboard commercial aircraft.32 While the basis for these modifications was 

to mitigate risk, as shown in table 2, TSA senior leadership considered 

several other factors when deciding whether to implement the 

modifications. 

 32The SOP modifications made by TSA on August 10, 2006, August 12, 2006, September 26, 

2006, and November 21, 2006, were designed to address only one particular hydrogen 

peroxide-based liquid explosives mixture, which, according to TSA officials, was the same 

mixture that the alleged terrorists had planned to detonate on U.S.-bound flights originating

in the United Kingdom. DHS and FBI have identified additional liquid explosives mixtures

that could pose a threat to commercial aviation. DHS has ongoing evaluations of the 

additional mixtures to determine their explosive potential and the extent of damage that

detonation of these mixtures could cause to an aircraft. DHS is also evaluating explosives 

detection technology to determine the extent to which it can be used at the checkpoint to 

defend against the liquid explosives threat. We are currently evaluating DHS’s and TSA’s 

progress in planning for, managing, and deploying research and development programs in

support of airport checkpoint screening operations. We expect to report on our results in

August 2007. 

Page 21 GAO-07-634 Aviation Security
Table 2: Factors Considered by TSA When Deciding How to Modify Passenger Checkpoint Screening SOPs in Response to 

the Alleged August 2006 Terrorist Plot to Detonate Liquid Explosives on U.S.-Bound Aircraft 

Procedures Impact on security 

August 10, 2006: Total ban on liquids and gels in accessible property or 

onboard aircraft. Exceptions: 

• baby formula/milk if infant is traveling; 

• prescription medication with name matching passenger’s ticket; 

• insulin and other essential nonprescription medications; 

• liquids and gels carried by passengers with disabilities, after screening 

for explosive materials, with Supervisory TSO/Screening Manager 

concurrence; 

• supplies brought into retail area by approved vendors for restocking of 

retail operations. 

Passengers required to remove shoes at checkpoints for X-ray screening.

 

Benefits 

• Terrorists less likely to successfully carry liquid 

explosives onto aircraft using container. 

• Terrorists less likely to successfully carry liquid 

explosives onto aircraft in shoes (e.g., gel-based 

insoles). 

Drawbacks 

• None identified

August 12, 2006a: Aerosols prohibited. Following additional items allowed 

past checkpoints: 

• baby food in small containers, if baby/small child is traveling; 

• essential nonprescription medications (e.g., contact lens saline solution, 

eye care products), not to exceed 4 fluid ounces per container; 

• liquids and gels for diabetic passengers, no greater than 8 fluid ounces 

per container; 

• gels, saline solutions, and other liquids used to augment portions of 

body for medical/cosmetic reasons; 

• life support/life sustaining liquids (e.g., bone marrow and blood 

products. 

Benefits 

• Terrorists less likely to successfully carry liquid 

explosives onto aircraft using container. 

• Terrorists less likely to successfully carry liquid 

explosives onto aircraft in shoes (e.g., gel-based 

insoles). 

Drawbacks 

• None identified

Page 22 GAO-07-634 Aviation Security
Impact on efficiency of screening

process Impact on customer service Other considerations

Benefits 

• Requiring passengers to remove 

footwear will speed the screening 

process by reducing the need to ETD 

and physically inspect footwear. 

Footwear now only needs to be

subjected to physical search if 

something suspicious appears on the 

X-ray of the shoes. 

Drawbacks 

• Total ban on liquids and gels may be 

unsustainable for long term because 

more passengers would check their 

baggage rather than carry it on, 

which would cause a strain on the 

checked baggage screening system. 

Benefits 

• Exceptions allow passengers with 

legitimate medical and other needs to 

bring essential liquids onboard aircraft. 

• Passengers less confused about whether 

to remove shoes for X-ray screening. 

Drawbacks 

• Inconvenient for passengers to not be 

able to carry toiletries and similar liquids 

and gels onto planes. 

• Threat was a specific type of liquid 

explosive. 

• There was no checkpoint screening 

technology available for deployment that 

could detect the specific liquid explosive. 

Benefits 

• Requiring passengers to remove 

footwear will speed the screening 

process by reducing the need to ETD 

and physically inspect footwear. 

Footwear now only needs to be

subjected to physical search if 

something suspicious appears on the 

X-ray of the shoes. 

Drawbacks 

• Total ban on liquids and gels may be 

unsustainable for long term because 

more passengers would check their 

baggage rather than carry it on, 

which would cause a strain to the 

checked baggage screening system. 

Benefits 

• Clarified for TSOs types and amounts of 

liquids and gels exempt from ban. 

• Created smoother process at checkpoint, 

minimizing impact upon travelers. 

• Gave diabetic passengers access to 

essential liquids. 

• Lifted prohibition against critical life 

saving fluids. 

Drawbacks 

• None identified

• Feedback from TSA field staff and industry 

representatives regarding exemptions 

associated with liquids, gels, and aerosols 

restrictions and specific information on the 

quantities of certain types of liquids, gels, 

and aerosols that should be exempted

from the restrictions. 

• Additional information was obtained about 

the alleged terrorist plot, including 

information from the United Kingdom and 

U.S. intelligence communities and 

discussions with explosives experts. 

Page 23 GAO-07-634 Aviation Security
Procedures Impact on security 

September 26, 2006: Liquids, gels, aerosols (not on prohibited items list 

or considered hazardous materials) permitted in accessible property in 3-

fluid ounce bottles fit comfortably in one quart-size, clear plastic, zip-top 

bag per passenger. Plastic bags screened by X-ray. Items purchased in 

sterile area of airports permitted onboard aircraft. 

Items allowed past checkpoints in amounts larger than 3 fluid ounces; 

must be declared and cleared by TSO:

• baby formula/milk /food in small containers if baby/small child is 

traveling, 

• medications (liquid, gel, aerosol), 

• liquids and gels for passengers indicating need to address diabetic or 

other medical condition. 

TSOs conducting declaration process positioned ahead of checkpoint to 

assess liquids, gels, and aerosols to determine reasonable quantity for 

passenger’s itinerary, and to advise passengers on procedures related to 

liquids, gels and aerosols that are either prohibited (requiring disposal or 

abandonment of items) or permitted but outside of plastic bag (TSO marks 

boarding pass or travel document to indicate items). 

Items newly permitted past checkpoints in any amount: 

• liquid, gel, and aerosol cleaning supplies required by airport employees 

servicing sterile area, 

• gels and frozen liquids required to cool any other items permitted past 

checkpoints, provided no unresolved suspicious items or activities. 

Random ETD sampling of plastic bags, containers within plastic bags, and

other containers holding liquids, gels, and aerosols. 

Benefits 

• Plastic bags present deterrent and operational 

complexities for terrorists—attempts to combine liquids 

increase probability of detection. 

• Requirement to remove and submit plastic bags for 

X-ray screening serves as deterrent to terrorists, and 

provides TSOs opportunity to view and examine all 

liquids, gels, and aerosols. 

• Plastic bags hinder terrorists from carrying large 

enough amounts of liquid explosives that could 

potentially cause catastrophic damage to an aircraft. 

• Declaration process thought to deter terrorists from 

attempting to carry liquid explosives onboard aircraft. 

• Random ETD sampling enables TSOs to determine 

whether the small amounts of liquids and gels being 

carried through the checkpoint are, in fact, explosives. 

This procedure may also deter terrorists from 

attempting to carry liquid explosives onboard aircraft. 

Drawbacks 

• Possibility that terrorists could combine liquids in small 

bottles to generate an amount large enough to

potentially cause catastrophic damage to an aircraft. 

• The additional drawbacks related to the impact on 

security are sensitive security information. Therefore, 

we do not discuss those drawbacks in this report. 

Page 24 GAO-07-634 Aviation Security
Impact on efficiency of screening

process Impact on customer service Other considerations

Benefits 

• Enables TSOs to focus resources on 

detecting explosives, rather than 

small amounts of liquids and gels that 

do not represent serious threat. 

• Checked baggage screening 

expected to return to sustainable 

levels. 

• Requirement to remove and submit 

plastic bags for X-ray screening

encourages passengers to reduce 

clutter in bags, making it easier for 

TSOs to screen for prohibited and 

threat items. 

Drawbacks 

• Increase in number of items X-rayed 

per passenger, which may slow down 

screening process. 

Benefits 

• Procedures easily learned by public and 

TSOs. 

• Accommodates many passengers with 

legitimate needs for small quantities of 

liquids during flights. 

Drawbacks 

• Possible negative public reaction to 

passengers having to provide their own 

plastic bags. 

• The results of liquid explosives tests 

conducted by DHS and the FBI. The 

results of these tests are sensitive security 

information and are not discussed in this 

report. 

• TSA gathered data to test its assumption 

regarding sustainability of the total ban on

liquids, gels, and aerosols and found that 

following the total ban, there was 

approximately a 27 percent increase in the 

number of bags checked per passenger. 

Page 25 GAO-07-634 Aviation Security
Procedures Impact on security 

November 21, 2006: Same as the procedures implemented on 

September 26, 2006, with the exception of the following: 

Liquids, gels, and aerosols allowed in 3.4-fluid-ounce (100-milliliter) “travel

size” bottles. 

Declaration process eliminated; TSA employee ahead of checkpoint offers 

public advisements and assessments on procedures. 

(Additional modifications were made to the liquids, gels, and aerosols 

screening procedures. However, these additional modifications are 

sensitive security information. Therefore, we do not discuss these 

modifications in this report.) 

Benefits 

No additional security benefits identified. 

Drawbacks 

No additional drawbacks to security identified. 

Source: GAO analysis of TSA documentation

a

The August 12, 2006, SOP change incorporates clarifications implemented on August 16, 2006. 

Page 26 GAO-07-634 Aviation Security
Impact on efficiency of screening

process Impact on customer service Other considerations

Benefits 

• Elimination of the declaration process 

will reduce unnecessary redundancy 

in the examination of exempted

liquids and gels, which previously 

occurred both prior to and following xray screening. 

(TSA identified additional efficiency 

benefits of this modification to the 

liquids, gels, and aerosols screening 

procedures. These additional benefits 

are sensitive security information. 

Therefore, we do not discuss these 

benefits in this report.) 

Drawbacks 

No additional efficiency drawbacks 

identified.

Benefits 

• Allowing for risk-based discretion on the 

part of Supervisory TSOs enhances 

customer service for passengers who 

have legitimate reasons for carrying 

liquids, gels, or aerosols onboard planes. 

Drawbacks 

No additional customer service drawbacks 

identified. 

• The European Union allowed passengers 

to carry liquids, gels, and aerosols in travel 

sized containers up to 100 milliliters, 

approximately 3.4 fluid ounces. 

• The results of liquid explosive testing 

conducted by FBI and DHS. 

• TSA recognized that no procedure could 

be written to address every possible 

scenario involving liquids, gels, and 

aerosols. Therefore, TSA enabled 

Supervisory TSOs to use their discretion, 

while also considering security risks. 

Page 27 GAO-07-634 Aviation Security
As TSA senior leadership obtained more information about the particular 

threat posed by the liquid explosives through tests conducted by DHS’s 

Science and Technology Directorate and FBI, TSA relaxed the restrictions 

to allow passengers to carry liquids, gels, and aerosols onboard aircraft in

3-fluid-ounce bottles—and as of November 2006, 3.4-fluid-ounce bottles—

that would easily fit in a quart-sized, clear plastic, zip-top bag. TSA senior 

leadership identified both benefits and drawbacks to this SOP 

modification, but determined that the balance of security, efficiency, and 

customer service that would result from these SOP changes was 

appropriate. As shown in table 2, TSA officials recognize that there are 

security drawbacks—or vulnerabilities—associated with allowing 

passengers to carry even small amounts of liquids and gels onboard 

aircraft. For example, two or more terrorists could combine small 

amounts of liquid explosives after they pass through the checkpoint to 

generate an amount large enough to possibly cause catastrophic damage 

to an aircraft. However, TSA officials stated that doing so would be 

logistically challenging given the physical harm that the specific explosives

could cause to the person handling them, and that suspicion among 

travelers, law enforcement officials, and airport employees would likely be 

raised if an individual was seen combining the liquid contents of small 

containers stored in two or more quart-sized plastic bags. TSA officials 

stated that at the time of the modifications to the liquid, gels, and aerosols 

screening procedures, there was consensus among explosives detection 

experts, both domestically and abroad, regarding TSA’s assumptions about 

how the explosives could be used and the damage they could cause to an 

aircraft.33 TSA officials also stated that after reviewing the intelligence

information related to the alleged August 2006 London terror plot—

particularly with regard to the capability and intent of the terrorists—TSA

determined that allowing small amounts of liquids, gels, and aerosols 

onboard aircraft posed an acceptable level of risk to the commercial 

aviation system.34 Moreover, TSA officials acknowledged that there are 

vulnerabilities with allowing passengers to carry liquids that are exempted 

from the 3.4-fluid-ounce limit—such as baby formula and medication—

onboard aircraft. 

 33In February 2007, DHS Science and Technology directorate conducted aircraft 

vulnerability tests to determine the extent of damage the liquid explosives that were to be

used in the alleged August 2006 London terror plot would cause to an aircraft. The results

of these tests, however, are sensitive security information and are not included in this

report. 

34The intelligence information regarding the August 2006 London terror plot is classified 

and, therefore, is not included in this report. 

Page 28 GAO-07-634 Aviation Security
TSA officials stated that the enhancements TSA is making to the various 

other layers of aviation security will help address the security 

vulnerabilities identified above. For example, TSA has increased 

explosives detection canine patrols, deployed Federal Air Marshals on 

additional international flights, increased random screening of passengers 

at boarding gates, and increased random screening of airport and TSA 

employees who pass through the checkpoint. TSA also plans to expand 

implementation of its Screening Passengers by Observation Technique 

(SPOT) to additional airports. SPOT involves specially trained TSOs 

observing the behavior of passengers and resolving any suspicious 

behavior through casual conversation with passengers and referring 

suspicious passengers to selectee screening.35 TSA intends for SPOT to 

provide a flexible, adaptable, risk-based layer of security that can be

deployed to detect potentially high-risk passengers based on certain 

behavioral cues. 

TSA’s Analysis of the 

Impact of Certain 

Proposed Screening 

Changes on Security and 

TSO Resources Could Be 

Strengthened 

While professional judgment regarding risk factors, experience in the 

operating environment, and customer feedback have guided many of the

decisions TSA leadership made about which screening procedures to 

implement, TSA also sought to use empirical data as a basis for evaluating

the impact some screening changes could have on security and TSO 

resources. The TSA Assistant Secretary stated in December 2005 that TSA 

sought to make decisions about screening changes based on data and

metrics—a practice he said TSA would continue. The use of data and 

metrics to inform TSA’s decision making regarding implementing 

proposed screening procedures is consistent with our prior work that has 

shown the importance of data collection and analyses to support agency 

decision making. Between October 2005 and January 2006, TSA’s 

Explosives Detection Improvement Task Force sought to collect data as 

part of an effort to test the impact of seven proposed procedures at 

selected airports, as noted earlier.36 These seven proposed procedures 

were selected because officials believed they would have a significant 

impact on how TSOs perform daily screening functions, TSO training, and

 35In the event that TSOs cannot determine the reason for a passenger’s suspicious behavior, 

the TSO refers the passenger to law enforcement officials. TSA officials responsible for

SPOT told us that in designing the implementation of SPOT, they worked closely with FBI 

staff, Secret Service staff, Israeli security experts, and state police with experience in 

recognizing suspicious behaviors. 

36Another SOP change was operationally tested and subsequently rejected. TSA did not 

provide documentation or other information on the reason it was rejected. 

Page 29 GAO-07-634 Aviation Security
customer acceptability. According to TSA’s chief of security operations, 

the purpose of testing these procedures in the airport environment was to 

ensure that TSA was “on the right path” in implementing them. These 

particular procedures were considered by senior TSA officials as 

especially important for enhancing the detection of explosives and for 

deterring terrorists from attempting to carry out an attack. According to 

TSA, some of the proposed procedures could also free up TSOs so that 

they could spend more time on procedures for detecting explosives and 

less time on procedures associated with low security risks, such as 

identifying small scissors in carry-on bags. The seven proposed 

procedures tested by the task force reflect both new procedures and 

modifications to existing procedures, as shown in table 3. 

Page 30 GAO-07-634 Aviation Security
Table 3: Proposed Procedures Operationally Tested by the Explosives Detection Improvement Task Force, October 2005-

January 2006

Title of proposed

procedure

New or revised

procedure Previous procedure Proposed procedure 

Screening 

Passengers by

Observation 

Techniquea

 

New N/A Designated TSOs will observe the behavioral

patterns of passengers, and based on their 

observations, TSOs will conduct casual 

conversations, refer suspicious passengers to 

secondary screening, and in some cases refer 

some individuals to law enforcement officers

Unpredictable 

Screening 

Process (USP)

Revised Selectee, or additional, screening of 

passengers must be conducted 

continuously. If the number of individuals 

that alarm the walk-through metal detector 

or if the number of bags that alarm is not 

enough to ensure continual additional 

screening, individuals and bags must be 

randomly selected to meet this requirement. 

Random selectee screening is to be replaced by 

the USP, which entails random selection of 

passengers across two screening lanes to be

subjected to a predetermined element of the 

selectee screening process. The specific 

elements are sensitive security information and 

are not discussed in this report. 

Bulk-item patdown search Revised The pat-down procedure included only the 

torso area of the body. 

The pat-down is to include not only the torso, but 

also from the waistline down. 

IED components 

search 

New N/A TSOs are to implement additional measures if

they find an IED component, such as a battery, 

when screening. 

Selectee 

screening 

changes 

Revised There was a rigid set of procedures for 

resolving alarms set off by selectees. 

More flexibility is to be provided for resolving 

alarms set off by selectees. 

Threat area 

search 

Revised For bags that appear to pose a security 

threat, various searches were conducted, 

where some of the searches were not 

directly focused on the reason for suspicion. 

For bags that appear to pose a security threat, 

the searches that are conducted are intended to 

focus more on the reason for suspicion. 

Prohibited items 

list changes 

Revised Scissors (metal with pointed tips, except 

ostomy scissors with pointed tips with an

overall length, including blades and handle, 

of 4 inches or less, when accompanied by 

an ostomate supply kit containing related

supplies, such as collection pouches, 

wafers, positioning plates, tubing, or 

adhesives) and tools (including, but not 

limited to, wrenches and pliers) were not 

permitted on aircraft. 

Allow scissors with pointed tips and blades less 

than 4 inches and tools less than 7 inches in 

length onto aircraft. 

Source: TSA 

Note: N/A stands for “not applicable,” meaning that no previous procedure existed prior to the new 

procedure. 

a

Implementation of SPOT did not involve a revision to the passenger checkpoint screening SOP; 

rather, TSA developed a separate set of standard operating procedures for SPOT. However, we 

included SPOT in our review because it modifies the way in which TSOs screen passengers and their 

carry-on items at the checkpoint. 

Page 31 GAO-07-634 Aviation Security
Our analysis of TSA’s data collection and data analysis for the seven 

procedures that were operationally tested identified several problems that 

affected TSA’s ability to determine whether these procedures, as designed 

and implemented by TSA, would have the intended effect—to enhance the 

detection of explosives during the passenger screening process or to free 

up resources so that explosives detection procedures could be

implemented. Although the deterrence of persons intending to do harm is 

also an intended effect of some proposed SOP modifications, TSA officials 

said that it is difficult to assess the extent to which implementation of 

proposed procedures would deter terrorists. The Office of Management 

and Budget has also acknowledged the difficulty in measuring deterrence,

particularly for procedures intended to prevent acts of terrorism. While we 

agree that measuring deterrence is difficult, opportunities exist for TSA to 

strengthen its analyses to help provide information on whether the 

proposed procedures would enhance detection or free up TSO resources, 

when intended. 

Screening Passengers by Observation Technique. TSA officials stated 

that SPOT is intended to both deter terrorists and identify suspicious 

persons who intend to cause harm while on an aircraft. While we 

recognize that it is difficult to assess the extent to which terrorists are 

deterred by the presence of designated TSOs conducting behavioral 

observations at the checkpoint, we believe that there is an opportunity to 

assess whether SPOT contributes to enhancing TSA’s ability to detect 

suspicious persons that may intend to cause harm on an aircraft. One 

factor that may serve as an indicator that a person intends to do harm on 

an aircraft is whether that individual is carrying a prohibited item. TSA 

collected and assessed data at 14 airports for various time periods on the 

number of prohibited items found on passengers who were targeted under 

SPOT and referred to secondary screening or law enforcement officials.37

However, these data collection efforts, alone, did not enable TSA to 

determine whether the detection of prohibited items would be enhanced if

SPOT were implemented because TSA had no means of comparing 

whether persons targeted by SPOT were more likely to carry prohibited 

items than persons not targeted by SPOT. To obtain this information, the 

task force would have had to collect data on the number of passengers not 

targeted by SPOT that had prohibited items on them. This information 

 37SPOT was operationally tested at 1 airport beginning in December 2003, at 2 additional

airports beginning in October 2004, and at 2 other airports beginning in October 2005. The

remaining 9 airports began participating in the operational testing of SPOT in December

2005. 

Page 32 GAO-07-634 Aviation Security
could be used to determine whether a greater percentage of passengers 

targeted under SPOT are found to have prohibited items than those 

passengers who are not targeted by SPOT, which could serve as one 

indicator of the extent to which SPOT would contribute to the detection of 

passengers intending to cause harm on an aircraft. 

Although it has not yet done so, it may be possible for TSA to evaluate the 

impact of SPOT on identifying passengers carrying prohibited items. There 

is precedent in other federal agencies for evaluating the security benefits 

of similar procedures. For instance, U.S. Customs and Border Protection 

(CBP) within DHS developed the Compliance Examination (COMPEX) 

system to evaluate the effectiveness of its procedures for selecting 

international airline passengers for secondary screening. Specifically, 

COMPEX compares the percentage of targeted passengers on which 

prohibited items are found to the percentage of randomly selected 

passengers on which prohibited items are found. The premise is that 

targeting is considered to be effective if a greater percentage of targeted 

passengers are found to possess prohibited items than the percentage of

randomly selected passengers, and the difference between the two 

percentages is statistically significant.38 CBP officials told us in May 2006

that they continue to use COMPEX to assess the effectiveness of their 

targeting of international airline passengers.39 When asked about using a 

method such as COMPEX to assess SPOT, TSA officials stated that CBP 

and TSA are seeking to identify different types of threats through their 

targeting programs. CBP, through its targeting efforts, is attempting to 

identify passengers with contraband and unauthorized aliens, whereas 

TSA, through SPOT, is attempting to identify potential high-risk 

passengers. Additionally, in commenting on a draft of this report, DHS 

stated that, according to TSA, the possession of a prohibited item is not a 

good measure of SPOT effectiveness because an individual may not intend

to use a prohibited item to cause harm or hijack an aircraft. While it may

be possible for a terrorist to cause harm or hijack an aircraft without using 

a prohibited item, as in the case of the September 11 terrorist attacks,40

 38Statistically significant means that it is highly unlikely to obtain a difference of a given 

size or more by chance, assuming that there is actually no difference in the probability of 

finding prohibited items between targeted and randomly selected passengers.

39CBP officials could not comment on whether a similar methodology could be used by

TSA, since they were not familiar with the SPOT procedure. 

40Following the September 11 terrorist attacks, the items terrorists reportedly used to carry 

out the attacks—box cutters—were subsequently prohibited onboard aircraft. 

Page 33 GAO-07-634 Aviation Security
other terrorist incidents and threat information identify that terrorists who

carried out or planned to carry out an attack on a commercial aircraft 

intended to do so by using prohibited items, including explosives and 

weapons. Therefore, we continue to believe that comparing the percentage 

of individuals targeted and not targeted under SPOT on which prohibited 

items are found could be one of several potential indicators of the 

effectiveness of SPOT. Such a measure may be most useful with regard to 

the prohibited items that could be used to bring down or hijack an aircraft. 

TSA officials stated that the agency agrees in principle that measuring 

SPOT effectiveness, if possible, may provide valuable insights. 

Unpredictable Screening Process, Bulk-Item Pat-Down Search, and 

IED Component Search. We found that the task force also could have 

strengthened its efforts to evaluate the security impact of other proposed 

procedures—specifically, USP, the bulk-item pat-down search, and the 

IED component search. For all three of these procedures, the task force 

did not collect any data during the operational testing that would help 

determine whether they would enhance detection capability. TSA officials 

told us that they did not collect these data because they had a limited 

amount of time to test the procedures because they had to make SOP 

modifications quickly as part of the agency’s efforts to focus on higher 

threats, such as explosives, and the TSA Assistant Secretary’s goal of 

implementing the SOP modifications before the 2005 Thanksgiving holiday

travel season. Nevertheless, TSA officials acknowledged the importance of 

evaluating whether proposed screening procedures, including USP and the 

bulk-item pat-down, would enhance detection capability. TSA officials 

stated that covert testing has been used to assess TSOs’ ability to detect

prohibited items, but covert testing was not implemented during 

operational testing of proposed procedures. Office of Inspection officials

questioned whether covert testing could be used to test, exclusively, the

security benefit of proposed procedures, because TSO proficiency and the

capability of screening technology also factor into whether threat objects 

are detected during covert tests. Four of the five aviation security experts 

we interviewed acknowledged this limitation but stated that covert testing 

is the best way to assess the effectiveness of passenger checkpoint 

screening.41 In commenting on a draft of this report, DHS stated that, 

according to TSA, USP is intended to disrupt terrorists’ planning of an 

attack by introducing unpredictability into the passenger checkpoint 

 41The fifth expert we interviewed said that he was uncertain how to assess the 

effectiveness of passenger checkpoint screening procedures. 

Page 34 GAO-07-634 Aviation Security
screening process, and tools such as covert testing could not be used to 

measure the effectiveness of USP to this end. While we agree that covert 

testing may not be a useful tool to assess the impact USP has on disrupting 

terrorists’ plans and deterring terrorists from attempting to carry out an 

attack, we continue to believe that covert testing could have been used to

assess whether USP would have helped to enhance detection capability 

during the passenger screening process, which TSA officials stated was 

another intended result of USP. 

Although TSA did not collect data on the security impact of the USP and 

bulk-item pat-down procedures, the task force did collect data on the 

impact these procedures had on screening efficiency—the time required to 

perform procedures—and on the reaction of TSOs, FSDs, and passengers 

to the proposed procedures. These data indicated that the USP procedure 

took less time, on average, for TSOs to conduct than the procedure it 

replaced (the random continuous selectee screening process); the revised 

pat-down procedure took TSOs about 25 seconds to conduct; and that 

passengers generally did not complain about the way in which both 

procedures were conducted. 

With respect to operational testing of the IED component search 

procedure, TSA was unable to collect any data during the testing period 

because no IEDs were detected by TSOs at the airports where the testing 

took place. As with the USP and bulk-item pat-down procedures, TSA 

could have conducted covert tests during the operational testing period to 

gather simulated data for the IED search procedure, in the absence of 

actual data.

Selectee Screening Changes and Threat Area Search. Recognizing 

that some of the proposed procedures intended to enhance detection 

would require additional TSO resources, TSA implemented several 

measures aimed collectively at freeing up TSOs’ time so that they could 

focus on conducting more procedures associated with higher threats—

identifying explosives and suspicious persons. For example, TSA modified 

the selectee screening procedure and the procedure for searching carry-on 

items—the threat area search—in order to reduce screening time. During 

an informal pilot of these proposed procedures at 3 airports in November 

2005, TSA determined that the proposed selectee screening procedure 

would reduce search time of each selectee passenger, on average, by

about 1.17 minutes at these airports. TSA also determined through this 

study that the proposed threat area search, on average, took 1.83 minutes

to conduct at the participating airports, as compared to the existing target 

Page 35 GAO-07-634 Aviation Security
object search that took, on average, 1.89 minutes, and the existing whole 

bag search that took, on average, 2.37 minutes. 

Prohibited Items List Changes. Another measure TSA implemented to 

free up TSO resources to focus on higher threats involved changes to the 

list of items prohibited onboard aircraft. According to TSA, TSOs were 

spending a disproportionate amount of TSA’s limited screening resources 

searching for small scissors and small tools, even though, based on threat 

information and TSA officials’ professional judgment, such items no longer 

posed a significant security risk given the multiple layers of aviation 

security. TSA officials surmised that by not having to spend time and 

resources physically searching passengers’ bags for low-threat items, such 

as small scissors and tools, TSOs could focus their efforts on 

implementing more effective and robust screening procedures that can be

targeted at screening for explosives. 

To test its assumption that a disproportionate amount of TSO resources 

was being spent searching for small scissors and tools, TSA collected 

information from several sources. First, TSA reviewed data maintained in 

TSA’s Performance Management Information System (PMIS),42 which 

showed that during the third and fourth quarters of fiscal year 2005 

(a 6-month period), TSOs confiscated a total of about 1.8 million sharp 

objects other than knives or box cutters. These sharp objects constituted 

19 percent of all prohibited items confiscated at the checkpoint. Second,

based on information provided by FSDs, TSOs, and other screening 

experts, TSA determined that scissors constituted a large majority of the 

total number of sharp objects found at passenger screening checkpoints.

Third, TSA headquarters officials searched through confiscated items bins 

at 4 airports and found that most of the scissors that were confiscated had 

blades less than 4 inches in length. Based on these collective efforts, TSA 

concluded that a significant number of items found at the checkpoint were 

low-threat, easily identified items, such as small scissors and tools, and 

that a disproportionate amount of time was spent searching for these 

items—time that could have been spent searching for high-threat items, 

such as explosives. TSA also concluded that because TSOs can generally

easily identify scissors, if small scissors were no longer on the prohibited 

 42TSA’s Performance Management Information System is designed to collect, analyze, and 

report passenger and baggage screening performance data, such as wait times at selected 

airports, workload data, and the performance and utilization of passenger and baggage 

screening equipment. TSA headquarters uses PMIS data to support external reporting on 

performance and internal decision-making processes. 

Page 36 GAO-07-634 Aviation Security
items list, TSOs could avoid conducting time-consuming physical bag 

searches to locate and remove these items. 

While we commend TSA’s efforts to supplement professional judgment 

with data and metrics in its decision to modify passenger checkpoint 

screening procedures, TSA did not conduct the necessary analysis of the 

data collected to determine the extent to which the removal of small 

scissors and tools from the prohibited items list could free up TSO 

resources. Specifically, TSA did not analyze the data on sharp objects 

confiscated at the checkpoint along with other relevant factors, such as 

the amount of time taken to search for scissors and the number of TSOs at 

the checkpoint conducting these searches, to determine the extent to 

which TSO resources could actually be freed up. Based on our analysis of 

TSA’s data for the 6-month period, where we considered these other 

relevant factors, we determined that TSOs spent, on average, less than 

1 percent of their time—about 1 minute per day over the 6-month period—

searching for the approximately 1.8 million sharp objects, other than 

knives and box cutters, that were found at passenger screening 

checkpoints between April 2005 and September 2005.43 If the average 

amount of time TSOs spent searching for sharp objects per day over a 

6-month period was less than 1 minute per TSO, and sharp objects 

constituted just 19 percent of all prohibited items confiscated at 

checkpoints over this period, then it may not be accurate to assume that 

no longer requiring TSOs to search for small scissors and tools would 

significantly contribute to TSA’s efforts to free up TSO resources that 

could be used to implement other security measures. 

 43To conduct our analysis we used TSA data that showed (1) it takes, on average, about 

1.89 minutes to conduct a bag search that was initiated because a TSO identified a 

prohibited item (such as a pair of scissors) in the X-ray image of a carry-on bag—this 

average search time was derived from an informal TSA property search time study 

conducted at 9 airports—and (2) there were 28,785 actual full-time-equivalent (FTE) 

passenger screening TSOs during fiscal year 2005. One FTE is equal to 1 work year or 

2,080 nonovertime hours. To determine the number of minutes per day, on average, each

TSO spent searching for sharp objects found during the 6-month period, we took the

following steps. First, we calculated the total amount of time (in minutes) taken to conduct 

the searches by multiplying the number of sharp objects found (1,762,571) by the average

time to conduct targeted searches (1.89 minutes), assuming that one item was found per 

search. This totaled 55,521 hours. Next, we calculated the amount of time, on average, each

TSO spent searching for the sharp objects found by dividing 55,521 hours by 28,785 TSO 

FTEs. The result was 1.93 hours per TSO. Finally, we converted average hours per TSO to 

minutes and divided by 130 days—the number of days worked by a TSO for 26 weeks over

a 6-month period (assuming 5 work days per week at 8 hours per day). The result was an 

average of 0.89 minutes per day per TSO over the 6-month period. 

Page 37 GAO-07-634 Aviation Security
To further support its assertion that significant TSO resources would be 

freed up as a result of removing small scissors and tools from the list of 

prohibited items, TSA officials cited the results of an informal study 

conducted in October 2005—which was intended to provide a general idea 

of the types of prohibited items TSOs were finding as a result of their 

searches and how long various types of searches were taking TSOs to 

conduct. Specifically, according to the study conducted at 9 airports over a 

14-day period, TSA determined that 24 percent of items found during 

carry-on bag searches were scissors. However, based on data regarding 

the number of bags searched, removing scissors may not significantly 

contribute to TSA’s efforts to free up TSO resources.44

TSA conducted additional informal studies 30, 60, and 90 days after the 

prohibited items list change went into effect to determine whether the 

change had resulted in reductions in the percentage of carry-on bags that

were searched and overall screening time. However, we identified 

limitations in TSA’s methodology for conducting these studies.45 In 

February 2007, a TSA official stated that some FSDs interviewed several 

TSOs after the prohibited items list change went into effect, and these 

TSOs reported that the change did save screening time. However, TSA 

could not identify how many TSOs were interviewed, at which airports the 

TSOs were located, and how the TSOs were selected for the interview; nor 

did TSA document the results of these interviews. TSA also did not use 

random selection or representative sampling when determining which 

TSOs should be interviewed. Therefore, the interview results cannot be 

generalized.

TSA officials acknowledged that they could have made some 

improvements in the various analyses they conducted on the prohibited 

 44The number of bags searched is sensitive security information. 

45The results of the informal follow-on studies, which were conducted at 6 to 9 airports,

show that the percentage of carry-on bags searched increased slightly at the time of the 

30-day study, then decreased slightly at the time of the 60-day and 90-day studies, 

respectively. However, the results of these informal studies may not be reliable due to the

limitations in the methodology TSA used to conduct the studies. Specifically, TSA did not 

use a methodology that would control for factors other than the prohibited items list 

change that may influence the percentage of carry-on bags searched by TSOs. To do this, 

TSA would have had to develop a formal, systematic methodology for randomly selecting 

various times of day, location of checkpoints, number of checkpoints, and so on for data 

collection. By not controlling for such factors, TSA may not know the extent to which a 

reduction in the percentage of carry-on bags searched is due to the prohibited items list 

changes. 

Page 38 GAO-07-634 Aviation Security
items list change. However, they stated that they had to make SOP 

modifications quickly as part of the agency’s efforts to focus on higher 

threats, such as explosives, and the TSA Assistant Secretary’s goal of 

implementing the SOP modifications before the 2005 Thanksgiving holiday

travel season. Additionally, officials stated that they continue to view their 

decision to remove small scissors and tools from the prohibited items list 

as sound, particularly because they believe small scissors and tools do not 

pose a significant threat to aviation security. TSA officials also stated that

they believe the prohibited items list change would free up resources 

based on various sources of information, including the professional 

judgment of TSA airport staff, and their analysis of PMIS data on 

prohibited items confiscated at checkpoints. The TSA Assistant Secretary 

told us that even if TSA determined that the proposed SOP modifications 

would not free up existing TSO resources to conduct explosives detection 

procedures, he would have implemented the modifications anyway 

considering the added security benefit of the explosives detection 

procedures. Additionally, a TSA headquarters official responsible for 

airport security operations stated that to help strengthen the agency’s 

analysis of future proposed SOP changes, the agency plans to provide the 

Explosives Detection Improvement Task Force with the necessary 

resources to help improve its data collection and analysis. 

An additional measure intended to free up TSO resources46 involved 

changes to CAPPS rules.47 TSA’s assumption is that these changes could 

allow TSOs who were normally assigned to selectee screening duties to be 

reassigned to new procedures, such as USP, which may require new 

screening positions. (Both USP and SPOT require TSO positions: USP 

requires one screening position for every two screening lanes, while SPOT 

 46TSA officials told us that TSA’s Office of Intelligence assessed the potential impact each 

of these CAPPS changes would have on security and, based in its analysis, determined that

none of the CAPPS changes would compromise security. 

47Passengers can be selected for secondary screening through CAPPS or other 

TSA-approved processes, such as the Selectee List. CAPPS rules are sensitive security 

information and, therefore, are not discussed in this report. 

Page 39 GAO-07-634 Aviation Security
typically uses more than one screening position per ticket checker at the 

checkpoint.

48) 

According to FSDs we interviewed, the changes made to the prohibited 

items list and the CAPPS rules had not freed up existing TSO resources, as 

intended. Specifically, as of August 2006, 13 of 19 FSDs we interviewed at 

airports that tested USP or SPOT said that TSO resources were not freed 

up as a result of these changes. In addition, 9 of the 19 FSDs said that in 

order to operationally test USP or SPOT, TSOs had to work overtime, 

switch from other functions (such as checked baggage screening), or a 

screening lane had to be closed. TSA’s Explosives Detection Improvement 

Task Force reported that nearly all of the FSDs at airports participating in

operational testing of USP believed that the procedure had security value,49

though the task force also reported that 1 FSD dropped out of the 

operational testing program for USP due to insufficient staffing resources 

and another could only implement the procedure during off-peak travel 

periods. Additionally, most of the FSDs we interviewed stated that the 

changes to the prohibited items list and CAPPS rules did not free up TSOs, 

as intended, to better enable TSOs to take required explosives detection

training. Specifically, as of August 2006, of the 19 FSDs we interviewed at 

airports that implemented USP and SPOT, 13 said that they did not 

experience more time to conduct explosives training as a result of changes 

to the prohibited items list and CAPPS rules.50 Three of the 13 FSDs said 

that they used overtime to enable TSOs to take the explosives training. As 

previously stated, the TSA Assistant Secretary stated that even if existing

TSO resources are not freed up to conduct explosives detection 

procedures, longer lines and wait times at airport checkpoints are an 

acceptable consequence, considering their added security benefit. With 

 48Ticket checkers are aircraft operator or TSA employees who are positioned before the 

screening checkpoint to perform identification check and sterile area access 

responsibilities as required by TSA. For passengers, ticket checkers verify travel 

documents and make sure the identifying information on the travel document is consistent 

with the information on the individual’s personal identification documents (e.g., licenses,

passport, etc.). Ticket checkers are also responsible for directing passengers designated as 

selectees to the appropriate screening lane. For nonpassengers, ticket checkers verify 

required identification before allowing access to the sterile area. 

49The task force reported that 1 FSD was unsure of the security benefits provided by USP,

though this FSD did support the concept of introducing unpredictability into the screening

process. 

50Of the remaining 6 FSDs, 5 said that TSO resources were freed up as a result of the 

prohibited items list and CAPPS rules changes, and 1 was uncertain whether TSO 

resources were actually freed up. 

Page 40 GAO-07-634 Aviation Security
regard to explosives training, he stated that it is acceptable for FSDs to use 

overtime or other methods to ensure that all TSOs participated in the 

required explosives detection training. He further noted that even if one 

screening change does not free up TSO resources, all of the changes 

intended to accomplish this—when taken together—should ultimately 

help to redirect TSO resources to where they are most needed. 

TSA’s efforts to add data and metrics to its tool kit for evaluating the 

impact of screener changes are a good way to supplement the use of 

professional judgment and input from other experts and sources in making 

decisions about modifying screening procedures. However, TSA’s methods 

for data collection and analysis could be improved. We recognize the 

challenges TSA faces in evaluating the effectiveness of proposed 

procedures, particularly when faced with time pressures to implement 

procedures. However, by attempting to evaluate the potential impact of 

screening changes on security and resource availability, TSA could help 

support its decision making on how best to allocate limited TSO resources 

and ensure that the ability to detect explosives and other high-threat 

objects during the passenger screening process is enhanced.

Documentation of the 

Reasoning behind 

Proposed SOP 

Modifications Was 

Incomplete 

While we were able to assess TSA’s reasoning behind certain proposed 

SOP modifications considered during our review period, our analysis was 

limited because TSA did not maintain complete documentation of 

proposed SOP modifications. Documentation of the reasoning behind 

decisions to implement or reject proposed modifications was maintained 

in various formats, including spreadsheets developed by TSA officials, 

internal electronic mail discussions among TSA officials, internal 

memorandums, briefing slides, and reports generated based on the results 

of operational testing. TSA did improve its documentation of the proposed 

SOP modifications that were considered during the latter part of our 

9-month review period. Specifically, the documentation for the SOP 

modifications proposed under the Explosives Detection Improvement 

Task Force provided more details regarding the basis of the proposed 

modifications and the reasoning behind decisions to implement or reject 

the proposed modifications. 

Of the 92 proposed SOP modifications considered during our 9-month 

review period that TSA documented, TSA provided the basis for 72. More 

specifically, TSA documented the basis—that is, the information, 

experience, or event that encouraged TSA officials to propose an SOP 

modification—for 35 of the 48 that were implemented and for 37 of the 

44 that were not implemented. However, TSA only documented the 

Page 41 GAO-07-634 Aviation Security
reasoning behind TSA senior leadership’s decisions to implement or not 

implement proposed SOP modifications for 43 of 92 proposed 

modifications. According to TSA officials, documentation that explains the 

basis for recommending proposed modifications can also be used to 

explain TSA’s reasoning behind its decisions to implement proposed 

modifications. However, the basis on which an SOP modification was 

proposed cannot always be used to explain TSA senior leadership’s 

decisions not to implement a proposed modification. In these cases, 

additional documentation would be needed to understand TSA’s decision 

making. However, TSA only documented the reasoning behind its 

decisions for about half (26 of 44) of the proposed modifications that were 

not implemented. TSA officials told us that they did not intend to 

document all SOP modifications that were proposed during our review 

period. Officials stated that, in some cases, the reasoning behind TSA’s 

decision to implement or not implement a proposed SOP modification is

obvious and documentation is not needed. TSA officials acknowledged 

that it is beneficial to maintain documentation on the reasoning behind 

decisions to implement or reject proposed SOP modifications deemed 

significant, particularly given the organizational restructuring and staff 

turnover within TSA.51 However, TSA officials could not identify which of 

the 92 proposed SOP modifications they consider to be significant because

they do not categorize proposed modifications in this way. 

Our standards for governmental internal controls and associated guidance 

suggest that agencies should document key decisions in a way that is 

complete and accurate, and that allows decisions to be traced from 

initiation, through processing, to after completion.52 These standards 

further state that documentation of key decisions should be readily 

available for review. Without documenting this type of information, TSA 

cannot always justify significant modifications to passenger checkpoint 

screening procedures to internal or external stakeholders, including 

Congress and the traveling public. In addition, considering the ongoing

personnel changes, without sufficient documentation, future decision 

 51Since its inception in November 2001, TSA has had multiple Assistant Secretaries 

(originally titled Under Secretaries of Transportation for Security). In addition, between 

January 2005 and August 2006, TSA issued seven press releases regarding senior-level 

personnel changes within the agency. 

52GAO, Internal Control: Internal Control Management and Evaluation Tool,

GAO-01-1008G (Washington, D.C.: August 2001). 

Page 42 GAO-07-634 Aviation Security
makers in TSA may not know on what basis the agency historically made 

decisions to develop new or revise existing screening procedures. 

Following our 9-month review period, TSA continued to make efforts to 

improve documentation of agency decision making, as evidenced by

decisions regarding the August 2006 and September 2006 SOP 

modifications related to the screening of liquids and gels. For example, 

TSA senior leadership evaluated the actions taken by the agency between

August 7 and August 13, 2006, in response to the alleged liquid explosives

terrorist plot, in order to identify lessons learned and improve the agency’s

reaction to future security incidents. As a result of this evaluation, as 

shown in table 4, TSA made several observations and recommendations 

for improving documentation of agency decision making when considering 

modifications to screening procedures. 

Table 4: TSA Evaluation of Documentation of Agency Decisions Made between

August 7 and August 13, 2006, Regarding the Alleged Liquid Explosives Terrorist 

Plot 

Observations Recommendations for improvement

There was no tracking of the overall timing 

and progress of deliberations of the 

various decision options. 

Track and record key issues raised and the 

timing of deliberations. 

There was no formal tracking of the 

decision options that were discussed or 

the rationale that was used when selecting

among the various decision options. 

Formally document options discussed, 

decisions made, and the rationale behind 

the decisions. 

There were no formal requirements for the 

type of information that needed to be 

documented or the format used to 

document the information on agency 

decisions. 

For each decision that is made, standardize 

the type of information that should be 

documented and develop an appropriate 

mechanism to store the information. 

The documentation that was used to 

support agency decisions did not contain 

basic audit trail information, such as the 

origin of the document and how the 

document was used. This may prevent 

decision makers from understanding the 

relevancy of the documentation to agency 

decisions. 

For each document used to support agency 

decisions, identify the origin of the document 

and how the document was used by 

decision makers. 

Source: TSA. 

Documentation of TSA’s decisions regarding the September 26, 2006, 

modifications to the liquid screening procedures showed that TSA had 

begun implementing the recommendations in table 4. TSA’s 

documentation identified the various proposed liquid screening 

Page 43 GAO-07-634 Aviation Security
procedures that were considered by TSA, the benefits and drawbacks of 

each proposal, and the rationale behind TSA’s final decision regarding 

which proposal to implement. The documentation also tracked the timing

of TSA’s deliberations of each of the proposed liquid screening 

procedures. However, the documentation of TSA’s decisions was not 

always presented in a standard format, nor was the origin and use of 

supporting documentation always identified. TSA officials acknowledged 

that documentation of the September 2006 SOP modifications could have 

been improved and stated that efforts to improve documentation, through

implementation of the recommendations in table 4, will continue to be a 

high priority. 

TSA implemented a performance accountability system in part to 

strengthen its monitoring of TSO compliance with passenger checkpoint 

screening SOPs. Specifically, in April 2006, TSA implemented the 

Performance Accountability and Standards System (PASS) to assess the 

performance of all TSA employees, including TSOs.53 According to TSA 

officials, PASS was developed in response to our 2003 report that 

recommended that TSA establish a performance management system that 

makes meaningful distinctions in employee performance,54 and in response 

to input from TSA airport staff on how to improve passenger and checked 

TSA Has Several 

Methods in Place to 

Monitor TSO 

Compliance with 

Passenger Checkpoint 

Screening SOPs

A New Performance 

Accountability System 

Helps TSA Monitor TSO 

Compliance with SOPs 

 53In July 2005, prior to the implementation of PASS, TSA required all FSDs to implement an 

audit program of screening checkpoint operations, primarily focused on assessing TSO 

compliance with checkpoint screening SOPs. Specifically, each airport is to have an audit 

program that evaluates TSOs’ ability to detect threat objects taken through the checkpoint, 

as well as TSOs’ compliance with SOPs for screening passengers and their accessible 

property. The audit program is also intended to evaluate screening supervisors’ and lead

TSOs’ compliance with the SOP. 

54GAO-03-190. 

Page 44 GAO-07-634 Aviation Security
baggage screening measures. With regard to TSOs, PASS is not intended

solely to measure TSO compliance with SOPs. Rather, PASS will be used 

by TSA to assess agency personnel at all levels on various competencies, 

including training and development, readiness for duty, management 

skills, and technical proficiency. 

There are three elements of the TSO technical proficiency component of 

PASS that are intended to measure TSO compliance with passenger 

checkpoint screening procedures: (1) quarterly observations conducted by

FSD management staff of TSOs’ ability to perform particular screening 

functions in the operational environment, such as pat-down searches and

use of the hand-held metal detector, to ensure they are complying with 

checkpoint screening SOPs; (2) quarterly quizzes given to TSOs to assess 

their knowledge of the SOPs; and (3) an annual, multipart knowledge and

skills assessment. While the first two elements are newly developed, the 

third element—the knowledge and skills assessment—is part of the annual 

TSO recertification program that is required by the Aviation and 

Transportation Security Act (ATSA) and has been in place since October

2003.

55 Collectively, these three elements of PASS are intended to provide a 

systematic method for monitoring whether TSOs are screening passengers 

and their carry-on items according to SOPs. TSA’s implementation of PASS 

is consistent with our internal control standards, which state that agencies 

should ensure that policies and procedures are applied properly.56

The first component of PASS (quarterly observations) is conducted by 

screening supervisors or screening managers, using a standard checklist 

developed by TSA headquarters, with input from TSA airport staff. There 

is one checklist used for each screening function, and TSOs are evaluated 

on one screening function per quarter. For example, the hand-held metal

detector skills observation checklist includes 37 tasks to be observed, 

such as whether the TSO conducted a pat-down search to resolve any 

suspect areas. The second component of PASS (quarterly quizzes) consists 

of multiple-choice questions on the standard operating procedures. For 

example, one of the questions on the PASS quiz is “What is the correct 

place to start an HHMD outline [a hand-held metal detector search] on an

 55ATSA requires that each TSO receive an annual proficiency review to ensure he or she 

continues to meet all qualifications and standards required to perform screening functions. 

See 49 U.S.C. § 44935(f)(5). 

56GAO-01-1008G. 

Page 45 GAO-07-634 Aviation Security
individual: (a) top of the head, (b) top of the feet, or (c) top of the 

shoulder?” 

The third component of PASS is the annual knowledge and skills 

assessment, a component of the annual recertification program that 

evaluates the technical proficiency of TSOs. This assessment is composed 

of three modules: (1) knowledge of standard operating procedures, 

(2) recognition of threat objects on an X-ray image, and (3) demonstration 

of screening functions. According to TSA officials, while recertification 

testing is not a direct measure of operational compliance with passenger 

checkpoint screening SOPs, recertification testing, particularly module 1 

and module 3, is an indicator of whether TSOs are capable of complying 

with SOPs. TSA officials stated that if a TSO does not have knowledge of

SOPs and if the TSO cannot demonstrate basic screening functions as 

outlined in the SOPs, then the TSO will likely not be able to comply with 

SOPs when performing in the operating environment. Table 5 provides a 

summary of each of these modules. 

Table 5: Modules Included in Recertification Knowledge and Skills Assessment 

Testing module Description

Knowledge of standard operating 

procedures 

Computerized 50-question multiple-choice test. It is 

either passenger- or baggage-specific. 

Image recognition Computerized test that consists of 100 images and 

is used to evaluate a TSO’s skill and ability in

detecting threat or prohibited objects within X-ray 

images. 

Practical demonstration of skills Hands-on simulated work sample to evaluate a 

TSO’s knowledge, skills, and ability when performing 

specific screening tasks along with ability to provide 

customer service. 

Source: TSA. 

FSDs we interviewed reported that they have faced resource challenges in

implementing PASS. Specifically, as of July 2006, 9 of 24 FSDs we 

interviewed said they experienced difficulties in implementing PASS due 

to lack of available staff to conduct the compliance-related evaluations. 

TSA officials stated that they have automated many of the data-entry 

functions of PASS to relieve the field of the burden of manually entering

this information into the PASS online system. For example, all scores 

related to the quarterly quiz and skill observation components are 

automatically uploaded, and PASS is linked to TSA’s online learning center 

database to eliminate the need to manually enter TSOs’ learning history. In 

addition, the TSA Assistant Secretary said that FSDs were given the option 

Page 46 GAO-07-634 Aviation Security
of delaying implementation of PASS if they were experiencing resource 

challenges. 

TSA Uses Local and 

National Covert Testing, in 

Part, to Assess TSO 

Compliance with SOPs 

TSA also conducts local and national covert tests, which are used to 

evaluate, in part, the extent to which noncompliance with the SOPs affects 

TSOs’ ability to detect simulated threat items hidden in accessible 

property or concealed on a person. TSA first issued guidance on its local

covert testing program—known as Screener Training Exercises and 

Assessments (STEA)—in February 2004. STEA testing is conducted by

FSD staff at airports, who determine the frequency at which STEA tests 

are conducted as well as which type of STEA tests are conducted. 

According to the STEA results reported by TSA between March 2004 and

February 2006,57 TSOs’ noncompliance with the SOP accounted for some 

of the STEA test failures.58 TSOs’ lack of proficiency in skills or 

procedures, which may affect TSOs’ ability to comply with procedures, 

was also cited as the reason for some of the STEA test failures. TSOs who 

fail STEA tests are required to take remedial training to help them address 

the reasons for their failure. 

FSDs we interviewed reported that they have faced resource challenges in

conducting STEA tests. Specifically, even though all 24 FSDs we 

interviewed as of July 2006 said that they have conducted STEA tests, 

10 of these FSDs said that the lack of available staff made it difficult to 

conduct these tests. When asked how they planned to address FSDs’ 

concerns regarding a lack of available staff to complete STEA tests, TSA 

headquarters officials told us that they are considering resource 

alternatives for implementing the STEA program, but could not provide us

with the specific details of these plans.59 Until the resource limitations that 

have restricted TSA’s use of its compliance monitoring tools have been 

fully addressed, TSA may not have assurance that TSOs are screening 

passengers according to the SOP. 

 57As of February 2006, STEA test results had been recorded for a total of 417 airports. 

58The results of STEA testing are sensitive security information and, therefore, are not 

included in this report. 

59As of December 2006, TSA was in the process of modifying STEA into a performance

measurement program. TSA plans to implement the new STEA program during the second

quarter of fiscal year 2007. 

Page 47 GAO-07-634 Aviation Security
As previously discussed, TSA’s Office of Inspection initiated its national 

covert testing program in September 2002. National covert tests are 

conducted by TSA headquarters-based inspectors who carry simulated 

threat objects hidden in accessible property or concealed on their person 

through airport checkpoints, and in cases where TSOs fail to detect threat

objects, the inspectors identify the reasons for failure. During September

2005, TSA implemented a revised covert testing program to focus more on 

catastrophic threats—threats that can bring down or destroy an aircraft. 

According to Office of Inspection officials, TSOs may fail to detect threat

objects during covert testing for various reasons, including limitations in 

screening technology, lack of training, limitations in the procedures TSOs 

must follow to conduct passenger and bag searches, and TSOs’ 

noncompliance with screening checkpoint SOPs. Office of Inspection 

officials also said that one test could be failed due to multiple factors, and

that it is difficult to determine the extent to which any one factor 

contributed to the failure. TSOs who fail national covert tests, like those 

who fail STEA tests, are also required to take remedial training to help 

them address the reasons for failure.60

The alleged August 2006 terrorist plot to detonate liquid explosives 

onboard multiple U.S.-bound aircraft highlighted the need for TSA to 

continuously reassess and revise, when deemed appropriate, existing 

passenger checkpoint screening procedures to address threats against the 

commercial aviation system. In doing so, TSA faces the challenge of 

securing the aviation system while facilitating the free movement of 

people. Passenger screening procedures are only one element that affects 

the effectiveness and efficiency of the passenger checkpoint screening 

system. Securing the passenger checkpoint screening system also involves 

the TSOs who are responsible for conducting the screening of airline 

passengers and their carry-on items, and the technology used to screen 

passengers and their carry-on items. 

Conclusions 

We believe that TSA has implemented a reasonable approach to modifying 

passenger checkpoint screening procedures through its consideration of 

risk factors (threat and vulnerability information), day-to-day experience 

of TSA airport staff, and complaints and concerns raised by passengers 

and by making efforts to balance security, efficiency, and customer 

 60The covert testing results, including the reasons for failure, and the recommendations 

made by the Office of Inspection are classified and cannot be discussed in this report. 

Page 48 GAO-07-634 Aviation Security
service. We are also encouraged by TSA’s efforts to conduct operational 

testing and use data and metrics to support its decisions to modify 

screening procedures. We acknowledge the difficulties in assessing the 

impact of proposed screening procedures, particularly with regard to the 

extent to which proposed procedures would deter terrorists from 

attempting to carry out an attack onboard a commercial aircraft. However, 

there are existing methods, such as covert testing and CBP’s COMPEX—a 

method that evaluates the effectiveness of CBP’s procedures for selecting 

international airline passengers for secondary screening—that could be

used by TSA to assess whether proposed screening procedures enhance 

detection capability. It is also important for TSA to fully assess available 

data to determine the extent to which TSO resources would be freed up to

perform higher-priority procedures, when this is the intended effect. 

Without collecting the necessary data or conducting the necessary analysis

that would enable the agency to assess whether proposed SOP 

modifications would have the intended effect, it may be difficult for TSA to 

determine how best to improve TSOs’ ability to detect explosives and 

other high-threat items and to allocate limited TSO resources. With such 

data and analysis, TSA would be in a better position to justify its SOP 

modifications and to have a better understanding of how the changes 

affect TSO resources. Additionally, because TSA did not always document 

the basis on which SOP modifications were proposed or the reasoning 

behind decisions to implement or not implement proposed modifications,

TSA may not be able to justify SOP modifications to Congress and the 

traveling public. While we are encouraged that TSA’s documentation of its 

decisions regarding the SOP modifications made in response to the alleged 

August 2006 liquid explosives terrorist plot was improved compared to 

earlier documentation, it is important for TSA to continue to work to 

strengthen its documentation efforts. Such improvements would enable

TSA officials responsible for making SOP decisions in the future to 

understand how significant SOP decisions were made historically— 

a particular concern considering the restructuring and staff turnover 

experienced by TSA. 

As shown by TSA’s covert testing results, the effectiveness of passenger 

checkpoint screening relies, in part, on TSOs’ compliance with screening 

procedures. We are, therefore, encouraged by TSA’s efforts to strengthen

its monitoring of TSO compliance with passenger screening procedures. 

We believe that TSA has implemented a reasonable process for monitoring

TSO compliance and that this effort should assist TSA in providing 

reasonable assurance that TSOs are screening passengers and their 

carry-on items according to screening procedures. Given the resource 

challenges FSDs identified in implementing the various methods for 

Page 49 GAO-07-634 Aviation Security
monitoring TSO compliance, it will be important for TSA to take steps, 

such as automating PASS data entry functions, to address such challenges. 

To help strengthen TSA’s evaluation of proposed modifications to 

passenger checkpoint screening SOPs and TSA’s ability to justify its 

decisions to implement or not implement proposed SOP modifications, in

the March 2007 report that contained sensitive security information, we 

recommended that the Secretary of Homeland Security direct the 

Assistant Secretary of Homeland Security for TSA to take the following 

two actions: 

• when operationally testing proposed SOP modifications, develop sound 

evaluation methods, when possible, that can be used to assist TSA in 

determining whether proposed procedures would achieve their 

intended result, such as enhancing TSA’s ability to detect prohibited 

items and suspicious persons and freeing up existing TSO resources 

that could be used to implement proposed procedures, and 

• for future proposed SOP modifications that TSA senior leadership 

determines are significant, generate and maintain documentation to 

include, at minimum, the source, intended purpose, and reasoning 

behind decisions to implement or not implement proposed 

modifications. 

On March 6, 2007, we received written comments on the draft report, 

which are reproduced in full in appendix III. DHS generally concurred 

with our recommendations and outlined actions TSA plans to take to 

implement the recommendations. 

Recommendations for 

Executive Action 

Agency Comments 

and Our Evaluation 

DHS stated that it appreciates GAO’s conclusion that TSA has 

implemented a reasonable approach to modifying passenger checkpoint 

screening procedures through its assessment of risk factors, the expertise

of TSA employees, and input from the traveling public and other 

stakeholders, as well as TSA’s efforts to balance security, operational 

efficiency, and customer service while evaluating proposed changes. 

With regard to our recommendation to develop sound evaluation methods, 

when possible, to help determine whether proposed SOP modifications 

would achieve their intended result, DHS stated that TSA plans to make 

better use of generally accepted research design principles and techniques 

when operationally testing proposed SOP modifications. For example, 

Page 50 GAO-07-634 Aviation Security
TSA will consider using random selection, representative sampling, and 

control groups in order to isolate the impact of proposed SOP 

modifications from the impact of other variables. DHS also stated that 

TSA’s Office of Security Operations is working with subject matter experts 

to ensure that operational tests are well designed and executed, and 

produce results that are scientifically valid and reliable. As discussed in 

this report, employing sound evaluation methods for operationally testing 

proposed SOP modifications will enable TSA to have better assurance that 

new passenger checkpoint screening procedures will achieve their 

intended purpose, which may include improved allocation of limited TSO 

resources and enhancing detection of explosives and other high-threat 

objects during the passenger screening process. However, DHS stated, and 

we agree, that the need to make immediate SOP modifications in response 

to imminent terrorist threats may preclude operational testing of some 

proposed modifications. 

Concerning our recommendation regarding improved documentation of 

proposed SOP modifications, DHS stated that TSA intends to document 

the source, intent, and reasoning behind decisions to implement or reject 

proposed SOP modifications that TSA senior leadership deems significant. 

Documenting this type of information will enable TSA to justify significant 

modifications to passenger checkpoint screening procedures to internal 

and external stakeholders, including Congress and the traveling public. In

addition, considering the ongoing personnel changes TSA has 

experienced, such documentation should enable future decision makers in 

TSA to understand on what basis the agency historically made decisions to

develop new or revise existing screening procedures. 

In addition to commenting on our recommendations, DHS provided 

comments on some of our findings, which we considered and incorporated 

in the report where appropriate. One of DHS’s comments pertained to 

TSA’s evaluation of the prohibited items list change. Specifically, while 

TSA agrees that the agency could have conducted a more 

methodologically sound evaluation of the impact of the prohibited items 

list change, TSA disagrees with our assessment that the prohibited items 

list change may not have significantly contributed to TSA’s efforts to free 

up TSO resources to focus on detection of high-threat items, such as 

explosives. As we identified in this report, based on interviews with FSDs, 

airport visits to determine the types of items confiscated at checkpoints, 

and a study to determine the amount of time taken to conduct bag 

searches and the number of sharp objects collected as a result of these 

searches, TSA concluded that the prohibited items list change would free 

up TSO resources. DHS also stated that interviews with TSOs following 

Page 51 GAO-07-634 Aviation Security
the prohibited items list change confirmed that the change had freed up 

TSO resources. However, based on our analysis of the data TSA collected

both prior to and following the prohibited items list change, we continue 

to believe that TSA did not conduct the necessary analysis to determine 

the extent to which the removal of small scissors and tools from the 

prohibited items list would free up TSA resources. 

As agreed with your office, unless you publicly announce its contents 

earlier, we plan no further distribution of this report until 21 days from the 

date of this report. At that time, we will send copies of the report to the 

Secretary of the Department of Homeland Security, the TSA Assistant 

Secretary, and interested congressional committees as appropriate. We 

will also make copies available to others on request. 

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

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

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

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

listed in appendix IV. 

Cathleen A. Berrick 

Director, Homeland Security and Justice Issues 

Page 52 GAO-07-634 Aviation Security
Appendix I: Objectives, Scope and Appendix I: Objectives, Scope and Methodology 

Methodology 

To assess the Transportation Security Administration’s (TSA) process for 

modifying passenger checkpoint screening procedures and how TSA 

monitors compliance with these procedures, we addressed the following 

questions: (1) How and on what basis did TSA modify passenger screening 

procedures and what factors guided the decisions to do so? (2) How does 

TSA determine whether TSOs are complying with the standard procedures 

for screening passengers and their carry-on items? 

To address how TSA modified passenger screening procedures and what 

factors guided the decisions to do so, we obtained and analyzed 

documentation of proposed standard operating procedures (SOP) changes

considered between April 2005 and September 2005, as well as threat 

assessments and operational studies that supported SOP modifications.1

The documentation included a list of proposed changes considered, as 

well as the source, the intended purpose, and in some cases the basis for 

recommending the SOP modification—that is, the information, 

experience, or event that encouraged TSA officials to propose the 

modifications—and the reasoning behind decisions to implement or reject 

proposed SOP modifications. We also obtained documentation of the 

proposed SOP changes considered by TSA’s Explosives Detection 

Improvement Task Force, which was the deliberating body for proposed 

changes that were considered between October 2005 and December 2005.

We also reviewed and analyzed similar documentation for proposed SOP 

modifications considered between August 2006 and November 2006 in 

response to the alleged terrorist plot to detonate liquid explosives onboard

multiple aircraft en route from the United Kingdom to the United States. 

We included modifications to passenger checkpoint screening procedures

related to this particular event because they provided the most recent 

information available of TSA’s approach to modifying screening 

procedures in response to an immediate perceived threat to civil aviation.

The documentation included notes from internal meetings, slides for 

internal and external briefings on proposed SOP modifications, data on 

customer complaints and screening efficiency, and the results of liquid 

explosives testing conducted by the Department of Homeland Security 

(DHS) Science and Technology Directorate and the Federal Bureau of 

Investigation (FBI). We also obtained each revision of the passenger 

checkpoint screening SOP that was generated between April 2005 and 

 1

We began our review period in April 2005 to coincide with TSA’s consideration of

proposed SOP modifications related to the second major revision of the passenger 

checkpoint screening SOP since TSA’s inception. 

Page 53 GAO-07-634 Aviation Security
Appendix I: Objectives, Scope and 

Methodology 

December 2005 and August 2006 and November 2006,2 as well as 

accompanying documentation that highlighted all of the changes made in 

each revision. In addition, we met with TSA headquarters officials who 

were involved in the process for determining whether proposed passenger 

checkpoint screening procedures should be implemented. We also met 

with officials in the DHS Science and Technology Directorate as well as 

the FBI to discuss the methodology and results of their liquid explosives

tests, which were used to support TSA’s decisions to modify the SOP in 

September 2006. We also met with TSA Office of Inspection and DHS 

Office of Inspector General staff to discuss their covert testing at 

passenger checkpoints and the recommended changes to the passenger 

checkpoint screening SOP that were generated based on testing results. 

We also obtained and analyzed data and information collected by TSA on 

the proposed procedures that were evaluated in the operational 

environment. In addition, we met or conducted phone interviews with 

Federal Security Directors (FSD) and their management staff, including

Assistant FSDs and Screening Managers, and Transportation Security 

Officers (TSO) with passenger screening responsibilities, at 25 commercial 

airports to gain their perspectives on TSA’s approach to revising the 

passenger checkpoint screening SOP. We also met with officials from four 

aviation associations—the American Association of Airport Executives, 

Airports Council International, the Air Transport Association, and the 

Regional Airline Association—to gain their perspectives on this objective.

Finally, we met with five aviation security experts to obtain their views on 

methods for assessing the impact of proposed passenger checkpoint 

screening procedures. We selected these experts based on their depth of 

experience in the field of aviation security, employment history, and their 

recognition in the aviation security community. However, the views of 

these experts may not necessarily represent the general view of other 

experts in the field of aviation security. We compared TSA’s approach to 

revising its passenger checkpoint screening SOP with the Comptroller 

General’s standards for internal control in the federal government3

 and 

risk management guidance. 

To address how TSA determines whether TSOs are complying with the 

standard procedures for screening passengers and their carry-on items, we 

 2

We did not assess all of the proposed SOP modifications associated with the SOP revisions

issued between August 2006 and November 2006; rather, we only reviewed the proposed 

modifications associated with screening for liquids, gels, and aerosols. 

3 GAO/AIMD-00-21.3.1. 

Page 54 GAO-07-634 Aviation Security
Appendix I: Objectives, Scope and 

Methodology 

obtained documentation of compliance-related initiatives, including 

guidance, checklists, and SOP quizzes used to assess TSO compliance 

under the Performance Accountability and Standards System (PASS), and 

guidance provided to FSDs for developing local compliance audit 

programs. We also obtained the fiscal year 2005 recertification and 

Screener Training Exercises and Assessments (STEA) test results, which 

were used, in part, to assess TSO compliance with and knowledge of the 

passenger checkpoint screening SOP. In addition, we reviewed the results 

of covert testing conducted by TSA’s Office of Inspection, which were also

used, in part, to assess TSO compliance with the passenger checkpoint 

screening SOP. We assessed the reliability of the compliance-related data

we received from TSA, and found the data to be sufficiently reliable for 

our purposes. In addition, we interviewed TSA headquarters officials who 

were responsible for overseeing efforts to monitor TSO compliance with 

standard operating procedures. This included officials in the Office of 

Security Operations, Office of Human Capital, and the Office of 

Operational Process and Technology. Our audit work also included visits 

to or phone conferences with 25 airports, where we interviewed FSDs, 

members of their management teams, and Transportation Security 

Officers with passenger screening responsibilities.4

 However, the 

perspectives of these FSDs and their staff cannot be generalized across all

airports. In July 2006, we submitted two sets of follow-up questions to FSD 

staff, related to their experiences with implementing PASS and STEA tests. 

We also obtained documentation of local compliance audit programs from 

the FSD staff at several of these airports. We compared TSA’s approach 

for monitoring TSO compliance with the Comptroller General’s standards 

for internal control in the federal government.5

As previously mentioned, we conducted site visits and/or phone interviews

at 25 airports6

 (8 category X airports, 7 category I airports, 4 category II 

airports, 4 category III airports, and 2 category IV airports) to discuss 

issues related to TSA’s approach to revising the passenger checkpoint 

screening SOP, and the agency’s approach to monitoring TSO compliance 

 4

We visited 25 airports. However, we met with only 24 FSDs, as 1 FSD was responsible for

2 of the airports we visited. 

5

GAO/AIMD-00-21.3.1. 

6

The list of airports we visited is sensitive security information. Therefore, we do not

identify those airports in this report. 

Page 55 GAO-07-634 Aviation Security
Appendix I: Objectives, Scope and 

Methodology 

with the SOP.7 We visited 7 of these airports during the design phase of 

our study. These airports were selected based on variations in size and 

geographic location, and whether they were operationally testing any 

proposed passenger checkpoint screening procedures or passenger 

screening technology. We also selected 2 airports that participated in the 

Screening Partnership Program.8

 

After visiting the 7 airports during the design phase of our review, we 

selected an additional 15 airports to visit based on variations in size, 

geographic distribution, and performance on compliance-related 

assessments. Specifically, we obtained and analyzed fiscal year 2005 

Screener Training Exercise and Assessments results and fiscal year 2005 

recertification testing results to identify airports across a range of STEA 

and recertification scores. Additionally, we visited 3 additional airports 

that operationally tested the proposed Unpredictable Screening Process 

(USP) and the Screening Passengers by Observation Technique (SPOT) 

procedure. 

 7

TSA classifies the more than 400 commercial 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. 

8

The Aviation and Transportation Security Act (ATSA) required that TSA begin allowing 

commercial airports to apply to TSA to transition from a federal to a private screener

workforce. See 49 U.S.C. § 44920. To support this effort, TSA created the Screening 

Partnership Program to allow all commercial airports an opportunity to apply to TSA for 

permission to use qualified private screening contractors and private screeners. There are

currently 6 airports participating in the Screening Partnership Program, including Jackson 

Hole, Kansas City International, Greater Rochester International, San Francisco 

International, Sioux Falls Regional, and Tupelo Regional. 

Page 56 GAO-07-634 Aviation Security
Appendix I: Objectives, Scope and 

Methodology 

In July 2006, we received from 19 FSDs answers to follow-up questions on 

their experiences with implementing pilot testing of SPOT or USP. This 

included 14 FSDs that were not part of our initial rounds of interviews. 

Nine of these 14 FSDs were from airports that participated in SPOT pilots. 

The remaining 5 of 14 FSDs that were not part of our initial rounds of 

interviews were from airports that were participants in USP pilots. 

We conducted our work from March 2005 through March 2007 in 

accordance with generally accepted government auditing standards. 

Page 57 GAO-07-634 Aviation Security
Appendix II: Sources of SOP Changes Appendix II: Sources of SOP Changes 

Of the 92 proposed screening changes considered by TSA between April 

2005 and December 2005, 63 were submitted by TSA field staff, including

Federal Security Directors and Transportation Security Officers.1

 Thirty 

proposed screening changes were submitted by TSA headquarters 

officials. Last, TSA senior leadership, such as the TSA Assistant Secretary,

recommended 5 of the 92 proposed screening changes considered during 

this time period. One SOP modification was also proposed through a 

congressional inquiry. TSA’s solicitation of input from both field and 

headquarters officials regarding changes to the passenger checkpoint 

screening SOP was consistent with internal control standards,2

 which 

suggest that there be mechanisms in place for employees to recommend 

improvements in operations. 

The FSDs with whom we met most frequently identified periodic 

conference calls with the Assistant Secretary, the SOP Question and 

Answer mailbox, or electronic mail to Security Operations officials as the 

mechanisms by which they recommended changes to the SOP. The TSOs 

with whom we met identified their chain of command and the SOP 

Question and Answer mailbox as the primary mechanisms by which they 

submitted suggestions for new or revised procedures. According to TSA 

officials, the SOP mailbox entails FSDs and their staff, including TSOs, 

submitting suggestions, questions, or comments to TSA’s Security 

Operations division via electronic mail, either directly or through their 

supervisors. Submissions are then compiled and reviewed by a single 

Security Operations official, who generates responses to the questions that 

have clear answers. However, for submissions for which the appropriate

response is not obvious or for submissions that include a suggestion to 

revise the SOP, this official forwards the submissions to other Security 

Operations officials for further deliberation. SOP mailbox responses are 

provided to all TSA airport officials. If TSA headquarters revised a 

screening procedure based on a mailbox submission, the revision is noted 

in the mailbox response. 

Thirty of the screening changes considered by TSA between April 2005 and 

December 2005 were proposed by TSA headquarters officials, including 

 1

There were 10 SOP modifications that were proposed both by multiple sources. We 

attributed 9 of these proposed modifications to each of the relevant sources. TSA did not

identify the sources for the 1 remaining modification that was proposed by multiple 

sources. 

2

GAO/AIMD-00-21.3.1. 

Page 58 GAO-07-634 Aviation Security
Appendix II: Sources of SOP Changes 

Security Operations officials, who are responsible for overseeing 

implementation of checkpoint screening. According to Security 

Operations officials, they recommended changes to checkpoint screening 

procedures based on communications with TSA field officials and airport 

optimization reviews. Security Operations officials conduct optimization 

reviews to identify best practices and deficiencies in the checkpoint 

screening and checked baggage screening processes. As part of these 

reviews, Security Operations officials may also assess screening efficiency

and whether TSOs are implementing screening procedures correctly. 

Other TSA headquarters divisions also suggested changes to passenger 

checkpoint screening procedures. For example, the Office of Law 

Enforcement recommended that there be an alternative screening 

procedure for law enforcement officials who are escorting prisoners or 

protectees. Previously, all armed law enforcement officers were required 

to sign a logbook at the screening checkpoint, prior to entering the sterile 

area of the airport. The officials in the Office of Passengers with 

Disabilities also recommended changes to checkpoint screening 

procedures. For example, in the interest of disabled passengers, they 

suggested that TSOs be required to refasten all wheelchair straps and 

buckles undone during the screening process. 

Last, TSA senior leadership suggested 5 of the 92 procedural changes 

considered by TSA between April 2005 and December 2005. TSA senior 

leadership also proposed a procedure that would allow TSOs to conduct 

the pat-down procedure on passengers of the opposite gender at airports 

with a disproportionate ratio of male and female TSOs. 

Page 59 GAO-07-634 Aviation Security
Appendix III: Comments from the Department Appendix III: Comments from the of Homeland Security

Department of Homeland Security 

Page 60 GAO-07-634 Aviation Security
Appendix III: Comments from the Department 

of Homeland Security

Page 61 GAO-07-634 Aviation Security
Appendix III: Comments from the Department 

of Homeland Security

Page 62 GAO-07-634 Aviation Security
Appendix III: Comments from the Department 

of Homeland Security

Page 63 GAO-07-634 Aviation Security
Appendix IV: 

A

GAO Contact and Staff 

cknowledgments 

Page 64 GAO-07-634

Appendix IV: GAO Contact and Staff 

Acknowledgments 

Cathleen A. Berrick, (202) 512-3404 or berrickc@gao.gov 

In addition to the person named above, Maria Strudwick, Assistant 

Director; David Alexander; Christopher W. Backley; Amy Bernstein; 

Kristy Brown; Yvette Gutierrez-Thomas; Katherine N. Haeberle; 

Robert D. Herring; Richard Hung; Christopher Jones, Stanley Kostyla; and 

Laina Poon made key contributions to this report. 

GAO Contact 

Acknowledgments 

Aviation Security
GAO Related Products GAO Related Products 

Aviation Security: TSA's Staffing Allocation Model Is Useful for 

Allocating Staff among Airports, but Its Assumptions Should Be 

Systematically Reassessed. GAO-07-299. Washington, D.C.: February 

28, 2007 

Aviation Security: Progress Made in Systematic Planning to Guide Key

Investment Decisions, but More Work Remains. GAO-07-448T. 

Washington, D.C.: February 13, 2007.

Homeland Security: Progress Has Been Made to Address the 

Vulnerabilities Exposed by 9/11, but Continued Federal Action Is Needed 

to Further Mitigate Security Risks. GAO-07-375. Washington, D.C.: 

January 24, 2007. 

Aviation Security: TSA Oversight of Checked Baggage Screening 

Procedures Could Be Strengthened GAO-06-869. Washington, D.C.: 

July 28, 2006.

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

Deployment of Checked Baggage Screening Systems, but Funding 

Uncertainties Remain GAO-06-875T. Washington, D.C.: June 29, 2006. 

Aviation Security: Management Challenges Remain for the 

Transportation Security Administration’s Secure Flight Program. 

GAO-06-864T. Washington, D.C.: June 14, 2006. 

Aviation Security: Further Study of Safety and Effectiveness and Better

Management Controls Needed if Air Carriers Resume Interest in 

Deploying Less-than-Lethal Weapons. GAO-06-475. Washington, D.C.: 

May 26, 2006. 

Aviation Security: Enhancements Made in Passenger and Checked 

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

D.C.: April 4, 2006. 

Aviation Security: Transportation Security Administration Has Made

Progress in Managing a Federal Security Workforce and Ensuring 

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

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

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

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

Page 65 GAO-07-634 Aviation Security
GAO Related Products 

Aviation Security: Significant Management Challenges May Adversely 

Affect Implementation of the Transportation Security Administration’s 

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

Aviation Security: Federal Air Marshal Service Could Benefit from 

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

November 28, 2005. 

Aviation Security: Federal Action Needed to Strengthen Domestic Air 

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

Transportation Security Administration: More Clarity on the Authority 

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

September 23, 2005. 

Aviation Security: Flight and Cabin Crew Member Security Training 

Strengthened, but Better Planning and Internal Controls Needed. 

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

Aviation Security: Transportation Security Administration Did Not 

Fully Disclose Uses of Personal Information during Secure Flight 

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

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

July 22, 2005.

Aviation Security: Better Planning Needed to Optimize Deployment of 

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

July 13, 2005.

Aviation Security: Screener Training and Performance Measurement 

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

May 2, 2005.

Aviation Security: Secure Flight Development and Testing Under Way, 

but Risks Should Be Managed as System Is Further Developed. 

GAO-05-356. Washington, D.C.: March 28, 2005. 

Aviation Security: Systematic Planning Needed to Optimize the 

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

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

Page 66 GAO-07-634 Aviation Security
GAO Related Products 

Aviation Security: Measures for Testing the Effect of Using Commercial

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

February 23, 2005. 

Transportation Security: Systematic Planning Needed to Optimize 

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

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

Airports to Use Private Passenger and Baggage Screening Services. 

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

General Aviation Security: Increased Federal Oversight Is Needed, but 

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

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

Aviation Security: Further Steps Needed to Strengthen the Security of 

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

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

Transportation Security Administration: High-Level Attention Needed 

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

May 28, 2004. 

Aviation Security: Challenges in Using Biometric Technologies. 

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

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

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

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

Aviation Security: Private Screening Contractors Have Little Flexibility 

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

April 22, 2004. 

Aviation Security: Improvement Still Needed in Federal Aviation 

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

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

D.C.: March 17, 2004. 

Page 67 GAO-07-634 Aviation Security
GAO Related Products 

Aviation Security: Factors Could Limit the Effectiveness of the 

Transportation Security Administration’s Efforts to Secure Aerial 

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

Aviation Security: Computer-Assisted Passenger Prescreening System 

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

D.C.: February 13, 2004. 

Aviation Security: Challenges Exist in Stabilizing and Enhancing 

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

D.C.: February 12, 2004. 

The Department of Homeland Security Needs to Fully Adopt a 

Knowledge-based Approach to Its Counter-MANPADS Development 

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

Aviation Security: Efforts to Measure Effectiveness and Strengthen 

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

Aviation Security: Federal Air Marshal Service Is Addressing Challenges 

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

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

Aviation Security: Efforts to Measure Effectiveness and Address 

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

Airport Passenger Screening: Preliminary Observations on Progress 

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

September 24, 2003. 

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

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

Transportation Security: Federal Action Needed to Enhance Security 

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

Transportation Security: Federal Action Needed to Help Address 

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

Federal Aviation Administration: Reauthorization Provides 

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

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

Page 68 GAO-07-634 Aviation Security
GAO Related Products 

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

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

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

February 25, 2003. 

Transportation Security Administration: Actions and Plans to 

Build a Results-Oriented Culture. GAO-03-190. Washington, D.C.: 

January 17, 2003. 

Aviation Safety: Undeclared Air Shipments of Dangerous Goods 

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

January 10, 2003. 

Aviation Security: Vulnerabilities and Potential Improvements for the 

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

Aviation Security: Registered Traveler Program Policy and 

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

22, 2002. 

Airport Finance: Using Airport Grant Funds for Security Projects Has 

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

October 15, 2002. 

Commercial Aviation: Financial Condition and Industry Responses 

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

Aviation Security: Transportation Security Administration Faces 

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

July 25, 2002.

Aviation Security: Information Concerning the Arming of Commercial

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

Aviation Security: Vulnerabilities in, and Alternatives for, Preboard 

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

September 25, 2001. 

Aviation Security: Weaknesses in Airport Security and Options for 

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

September 21, 2001. 

Page 69 GAO-07-634 Aviation Security
GAO Related Products 

Homeland Security: A Framework for Addressing the Nation’s 

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

Aviation Security: Terrorist Acts Demonstrate Urgent Need to Improve 

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

September 20, 2001. 

Aviation Security: Terrorist Acts Illustrate Severe Weaknesses in 

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

(440600) Page 70 GAO-07-634 Aviation Security
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