Aviation Security Technologies and Procedures: Screening Passengers and Baggage

Aviation Security Technologies and Procedures: Screening Passengers and Baggage

Order Code RL31151
CRS Report for Congress
Received through the CRS Web
Aviation Security Technologies and Procedures:
Screening Passengers and Baggage
Updated October 26, 2001
Daniel Morgan
Analyst in Science and Technology
Resources, Science, and Industry Division
Congressional Research Service ˜ The Library of Congress

Aviation Security Technologies and Procedures:
Screening Passengers and Baggage
Summary
Following the terrorist attacks on September 11, 2001, there is intense
congressional interest in improving the security screening process for airline
passengers and their baggage. In the United States, screening is the responsibility of
the airlines, which generally contract the work out to screening companies. The
Federal Aviation Administration has regulatory authority, deploys security equipment
in airports, and conducts research and development on security technology. The
current screening process includes technologies and procedures for screening
passengers themselves, their carry-on baggage, and their checked baggage. In each
of these areas there are technology options for improving the process. A key issue is
the performance of screener personnel. Issues of congressional interest include ways
to improve screener performance, possibly including federalization; funding and
oversight of the security equipment deployment program; and funding and oversight
of security technology development efforts. Congress has begun to consider several
bills in this area that have been introduced since the September 11 attacks, as well as
Administration proposals and actions. This report will be updated as circumstances
warrant.

Contents
Recent Congressional Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
The Current Screening Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Technology Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Passenger Screening Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Carry-on Baggage Screening Technologies . . . . . . . . . . . . . . . . . . . . . . . . 4
Checked Baggage Screening Technologies . . . . . . . . . . . . . . . . . . . . . . . . . 4
Screener Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Congressional Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Improving Screener Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Equipment Deployment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
New Technology Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
List of Tables
Table 1. FAA Budget for Aviation Security R&D . . . . . . . . . . . . . . . . . . . . . . . 8
Table 2. Bills to Improve Aviation Security Introduced
Since September 11, 2001 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Aviation Security Technologies and
Procedures: Screening Passengers and
Baggage
On September 11, 2001, three U.S. airliners were hijacked and used in terrorist
attacks on the Pentagon and the World Trade Center. A fourth hijacked airliner
crashed into a field in Pennsylvania. The hijackers were armed with knives, and
possibly other weapons, that had been smuggled into the aircraft passenger
compartments. As a result of these attacks, there is intense congressional interest in
improving the security screening process for airline passengers and their baggage.
This report describes current procedures and discusses potential technological
solutions, the key issue of screener performance, and some congressional options.
Other important aspects of aviation security, such as controlling access to secure
areas of airports, hardening aircraft against explosions, and securing cockpits against
hijackers, are not addressed in this report. Some of these other aspects are addressed
in the CRS Terrorism Briefing Book.1
Recent Congressional Action
Since the September 11 attacks, numerous bills have been introduced to improve
aviation security. The option most frequently addressed is federalization of the
screening process. Other provisions include screener training and employment
requirements, utilization of screening equipment, and research on improved
technologies and procedures. (See Table 2 at the end of this report). On September
27, 2001, the President announced that he will “work with Congress to put the federal
government in charge of airport security and screening services, including the
purchase and maintenance of all equipment.”2 On October 11, 2001, the Senate
passed S. 1447, the Aviation Security Act. The House of Representatives is expected
to take up aviation security legislation during the week of October 29, 2001. For
more information on current legislation, see CRS Report RL31150, Selected Aviation
Security Legislation in the Aftermath of the September 11 Attack.
The following committees have held hearings since the attacks to address
aviation security issues: House and Senate Appropriations Subcommittees on
Transportation (joint, September 20); Senate Committee on Commerce, Science, and
Transportation (September 20); Senate Committee on Government Affairs
1[http://www.congress.gov/brbk/html/ebter1.html]
2White House, Office of the Press Secretary, “Enhancing Aviation Safety and Security,”
September 27, 2001. [http://www.whitehouse.gov/news/releases/2001/09/20010927.html]

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(September 25); and House Committee on Transportation and Infrastructure,
Subcommittee on Aviation (October 11).
The Current Screening Process
In the United States, the airlines are responsible for screening passengers and
their baggage for security purposes. Except at small airports, airlines generally
contract with security companies to conduct the screening process. Screening is
regulated by the Federal Aviation Administration (FAA). In addition, since 1997, the
FAA has had a program to purchase certain security equipment and deploy it in
airports for use by the airlines and their security contractors. (See “Equipment
Deployment” below.) Airlines remain responsible for most of the cost of security
screening, however.
Security screening begins at check-in. First, computer-assisted passenger
prescreening (CAPPS) software uses classified criteria to identify certain passengers
as “selectees” for more intense scrutiny. In the past, some groups have expressed
concern that CAPPS may include discriminatory criteria such as race, national origin,
or appearance. The Department of Justice has reviewed the CAPPS criteria and has
determined that they do not consider such factors and are not discriminatory. Second,
passengers are asked a series of simple questions, such as whether they packed their
own bags. Often misunderstood, the purpose of these questions is to prevent “dupe”
attacks, in which a terrorist persuades a naive passenger to carry a dangerous item
unknowingly.
If a passenger checks baggage, it may be screened for bulk quantities of
explosives using x-ray computed tomography equipment similar to that used for
medical CAT scans. The availability and cost of this equipment, however, along with
the time it takes to screen a bag, do not currently permit its use in all airports, on all
flights at airports where it is used, or even on all bags on any given flight. To protect
against bombings by terrorists unwilling to commit suicide, the positive passenger-bag
matching (PPBM) procedure matches passengers with their checked bags, and bags
whose owners do not actually board the aircraft are removed before takeoff. PPBM
is used primarily on international flights.
The most familiar part of the screening process may be the security checkpoint
at which passengers and their carry-on bags are screened. Passengers themselves are
currently screened by walk-through metal detectors. If the detector alarms, screeners
use metal-detecting hand wands. Nonmetallic objects, including plastic and ceramic
weapons, will generally not be found by either procedure. At the same checkpoints,
carry-on bags are screened by equipment that displays an x-ray image of the bag
contents. An operator who sees a suspicious object in the image, or whose view is
blocked by a concealing object, may hand search a bag as a backup procedure.
Nonmetallic objects may be visible in the checkpoint x-ray image, but less clearly than
metal items, and operator training has up to now been focused on identifying metal
items. Carry-on baggage, especially laptop computers and other items that are difficult
to open for inspection, may also be screened with equipment that can detect the
chemical signature of trace quantities of explosives. Until the Secretary of

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Transportation directed otherwise on September 12, 2001, many small knives, such
as pocket knives, had been permitted on board even if detected by security personnel.
Technology Options
Technology options for making the security screening process more effective
include technologies for screening passengers, their carry-in baggage, and their
checked baggage. The cost of implementing new technologies and the question of
who will pay for them are issues of interest to policymakers.
Passenger Screening Technologies
As described above, current technologies for screening passengers are based on
metal detection. Equipment is available or under development in two other areas:
chemical trace detection, which can indicate whether a passenger has recently handled
explosives, and detection of nonmetallic threats, such as ceramic knives and plastic
guns. Trace-detecting portals look somewhat similar to walk-through metal detectors
and collect vapors and particles from the vicinity of the passenger for chemical
analysis. Equipment that can detect nonmetallic threats is based on imaging
technology that uses either backscattered x-rays or millimeter waves. Some prisons
and other high-security facilities already use some of these technologies.
For airport use on the general public, however, there are public acceptance issues
with any of these options. The images displayed by the imaging technologies, as well
as showing potential threat items, show the surface of the passenger’s body without
clothing. (It may be possible for software to block out parts of the image that do not
contain potential threat objects.) To collect the required chemical samples, some of
the trace-detection technologies use wands that make direct contact with the
passenger or air jets that can be felt and may disturb clothing. The capability to detect
concealed non-threat objects (such as drugs) may present legal issues regarding
unconstitutional search. Exposure of passengers to x-rays may raise health concerns.
These acceptance issues have been examined in detail by the National Research
Council (NRC).3
In a different approach, related in some ways to the CAPPS prescreening system
used at check-in, there has been renewed interest since the September 11 attacks in
the use of biometrics technology for passenger identification. In this category are
technologies based on fingerprints, retina scans, video face recognition, and other
techniques that could be used to match passengers against a database of individuals
who may pose a threat. Some of these technologies are already used at other types of
facilities, and a face recognition system has been installed in the airport in Reykjavik,
Iceland, but this would be a new approach for security in U.S. airports. As well as
deploying the technology, developing the database against which to make
comparisons would be a significant challenge. Civil liberties groups are concerned
about the legal implications of these technologies and the associated database.
3National Research Council, Airline Passenger Security Screening: New Technologies and
Implementation Issues (National Academy Press, Washington, 1996).

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Carry-on Baggage Screening Technologies
The x-ray equipment currently used to screen carry-on baggage can present a
cluttered image that makes the operator’s task difficult. To assist the operator, some
models take two images with x-rays of different energies, which allows them to
differentiate among materials and display a combined image that is color-coded by
whether an object is metallic, organic, and so on. Some use pattern-recognition
software to outline areas of a bag for closer attention by the operator. Some use
threat-image projection (TIP) to insert a stored image of a threat object into an actual
image of a bag, in order to help the operator stay alert (and to monitor performance).
Despite these techniques, it is difficult to identify nonmetallic objects with the
equipment currently used. Two existing technologies may be more capable in this
regard. First, some secure facilities already use backscatter x-ray equipment, which
creates a positive image from x-rays reflected from an object’s surface, rather than a
negative image from x-rays transmitted or absorbed in an object’s interior. Second,
the x-ray computed tomography equipment currently used on some checked baggage
can detect explosives and certain other nonmetallic items. Both these technologies,
especially the computed tomography type, are more expensive than existing
equipment, and computed tomography equipment is also much slower, which would
be a logistical challenge at a busy passenger checkpoint.
Checked Baggage Screening Technologies
The main purpose of screening checked baggage is the detection of bombs, since
potential hijackers cannot easily retrieve other items from the baggage hold during
flight. As noted above, x-ray computed tomography is the main technology in current
use. Some other techniques, such as chemical trace detection, are used to a lesser
extent (primarily to help resolve alarms). A variety of other technologies have been
explored by the FAA, equipment vendors, and others, but none has yet passed the
FAA certification requirements, which set standards for detection capability,
maximum frequency of false alarms, and throughput rate.4 (Detection of explosives
in checked baggage is the only aspect of screening for which the FAA has established
a certification procedure.) In addition, some alternative technologies, particularly
those based on nuclear techniques, present significant operational challenges for
airport use, such as size, weight, and radiation safety. The main emphasis of FAA
development efforts in this area has been improvement in the existing technologies,
particularly with regard to speed and cost, to enable screening of more bags in more
airports.
Screener Performance
FAA agents periodically test the performance of security personnel by posing as
passengers and attempting to carry potentially dangerous objects through airport
4See, for example, National Research Council, Detection of Explosives for Commercial
Aviation Security (National Academy Press, Washington, 1993).

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checkpoints. In these tests, screeners failed to detect the objects 13% of the time in
1978, 20% of the time in 1987, and even more frequently in the 1990s. Moreover,
screener performance declines further as tests become more realistic.5
One explanation for these performance levels is that rapid employee turnover
leads to a lack of experienced screeners. From May 1998 through April 1999,
screener turnover at the 19 largest U.S. airports averaged 126%, and at one airport,
it exceeded 400%.6 Low wages and lack of benefits are the most often cited reason
for such rapid turnover. Wages, for example, are often higher at airport fast-food
restaurants. Some analysts believe that other factors are equally important, including
the monotonous nature of the job, the stress of dealing with passengers who are
concerned about being late for their flights, and management issues.
In addition to turnover, a variety of human factors affect screener performance.
These include individual aptitude for the required tasks, sufficiency and effectiveness
of training, and individual ability to remain alert and vigilant for very rare events. FAA
initiatives such as pre-employment aptitude testing, computer-based training, and
threat-image projection technology are designed to address these issues.
Congressional Options
In responding to the September 11 attacks, Congress may consider actions in at
least three areas: improving screener performance, the FAA security equipment
deployment program, and the FAA security equipment research and development
(R&D) program.
Improving Screener Performance
Following the September 11 attacks, congressional attention has focused closely
on the screener performance issue. It was widely noted in congressional hearings and
in the press that most other countries place the responsibility for security with the
government or the airports, not with the airlines as in the United States.7 Based partly
on this fact and partly on the belief that a more unified approach would improve
coordination and funding, many analysts and policymakers have proposed
federalization of the screening process. (For a list of bills that address this option and
others, see Table 2. The term federalization means different things in different
proposals, including making screeners FAA employees, making them employees of
the Federal Protective Service, and making FAA responsible for screening but
permitting screeners to be employed by contractors.) An early cost estimate for
5General Accounting Office, Aviation Security: Terrorist Acts Illustrate Severe Weaknesses
in Aviation Security, GAO-01-1166T (September 20, 2001), p. 6. Test results since 1987
cannot be given here because they have been designated as sensitive security information.
6Ibid., p. 7.
7For further discussion of security operations in other countries, see ibid., p. 8, and General
Accounting Office, Aviation Security: Long-Standing Problems Impair Airport Screeners’
Performance, GAO/RCED-00-75 (June 2000).

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federalization was $1.8 billion per year, including wages for 28,000 full-time
employees, but the detailed assumptions built into this number were not immediately
known.8 Others suggested creation of an independent security organization, such as
a government-owned corporation. Still others emphasized raising standards for
performance and training over organizational questions. The Administration plan
released on September 27, 2001, called for screening and other security operations
to be performed by a combination of federal and nonfederal personnel, managed by
uniformed federal personnel.9 Based on a survey of airline and airport security
officials, the General Accounting Office has found a consensus that several different
options could improve screener performance, but that those surveyed disagree about
whether other operational criteria would be improved, unchanged, or made worse.10
The status of pending FAA security regulations may also be of interest as the
Congress considers the issue of screener performance. Revised security regulations
for airlines (14 CFR 108) were published in the Federal Register on July 17, 2001,
and are scheduled to take effect on November 14, 2001. In addition, proposed
regulations for certification of screening companies (14 CFR 111) were published in
the Federal Register on January 5, 2000. The Airport Security Improvement Act of
2000 (P.L. 106-528) required that the FAA issue a final rule on certification of
screening companies by May 31, 2001. Following some delays, the final rule was
nearly ready for release at the time of the September 11 attacks. In light of the
attacks, it has been put on hold and is being reexamined. The Congress may decide
to consider whether further changes in these regulations are needed, either to
strengthen them in light of the September 11 attacks or as part of broader
organizational changes in the security system.
Equipment Deployment
The September 11 attacks may intensify congressional interest in funding and
oversight of the FAA program for deployment of security equipment. This program
was begun in 1997, as directed by provisions in the Omnibus Consolidated
Appropriations Act of 1997 (P.L. 104-208) and the Federal Aviation Reauthorization
Act of 1996 (P.L. 104-264). Previously, airlines had been exclusively responsible for
purchasing and deploying their own security equipment. (They remain responsible for
some types of equipment and for maintenance and operating costs of equipment
purchased by the FAA.) The deployment program is conducted by the Security
Equipment Integrated Product Team (SEIPT), which includes members from airlines,
airports, and contractors as well as the FAA. Under the deployment plan developed
by the SEIPT, equipment is typically deployed first in the largest, busiest airports
(known as Category X airports), followed by smaller airports (Categories I through
IV). The FY2002 budget requested $97.5 million for purchase of equipment, plus
8Caroline E. Mayer, “Federalization of Airport Security Draws Debate,” Washington Post,
September 20, 2001.
9White House, Office of the Press Secretary, “Enhancing Aviation Safety and Security,”
September 27, 2001. [http://www.whitehouse.gov/news/releases/2001/09/20010927.html]
10General Accounting Office, Aviation Security: Vulnerabilities in, and Alternatives for,
Preboard Screening Security Operations, GAO-01-1171T (September 25, 2001).

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$2.5 million for related personnel and other expenses. Appropriations bills passed by
the House and Senate before the September 11 attacks (H.R. 2299 and S. 1178) both
provided the requested amount. There may be congressional interest in accelerating
or modifying the deployment program.
In considering the equipment deployment program, Congress may seek to
compare the security enhancement provided by different options. For example, at any
given funding level, what would be the most effective balance among new equipment
for screening checked baggage, for screening carry-on baggage, and for training
screeners? Until recently, there has been little evaluation of the security system’s
effectiveness at the system level, as opposed to the effectiveness of individual
technologies and procedures. A 1999 NRC report recommended development of a
“total architecture for aviation security” to permit measurement of the security
enhancement of the integrated system, both in its current configuration and in
alternative configurations. The report noted that “the urgent need for immediate
action”—a sense of urgency that is again felt in the wake of the September 11
attacks—had understandably resulted in equipment and procedures being
implemented rapidly without regard to overall architecture. It nevertheless concluded
that the total architecture concept is essential to a successful security system.11
New Technology Development
The FAA has a research and development program to develop new security
technologies. Located at the William J. Hughes Technical Center in Atlantic City,
New Jersey, this program conducts testing and evaluation and contracts with
companies and universities to conduct research and development on new
technologies. There are four program areas:
! explosives and weapons detection, to improve the performance, speed, and
cost of detection equipment;
! human factors, to optimize the interface between security equipment and its
human operators so that the combined system is most effective;
! aircraft hardening, to reduce or eliminate aircraft structural damage caused by
the detonation of bombs hidden in baggage; and
! airport security technology integration, to improve the integration of security
equipment into the airport operating environment.
The requested budget for this program in FY2002 is $50.3 million, somewhat
below the FY2001 level but roughly comparable with other recent years (see
Table 1). The House appropriations bill passed before the September 11 attacks
(H.R. 2299) reduced the request to $44.5 million, citing concerns about FAA
management. The Senate appropriations bill passed before the September 11 attack
(S. 1178) increased the request to $55.3 million to provide $5 million for development
of pulsed fast neutron analysis, a technology for detection of explosives in cargo.12 In
11National Research Council, Assessment of Technologies Deployed to Improve Aviation
Security: First Report (National Academy Press, Washington, 1999).
12The National Research Council is evaluating the practicality of using pulsed fast neutron
(continued...)

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light of the attacks on September 11, Congress may decide to expand the budget for
the aviation security R&D program. In addition, since the program’s primary
emphasis up to now has been on detection of explosives, the Congress may consider
increasing the emphasis on other threats, such as knives, guns, and other weapons that
might be used by hijackers.
Table 1. FAA Budget for Aviation Security R&D
($ in thousands)
Program Area
FY1998
FY1999
FY2000
FY2001
FY2002
Enacted
Enacted
Enacted
Enacted
Request
Explosives and Weapons
Detection
34,200
41,700
37,605
42,512
38,438
Human Factors
5,540
5,282
5,256
5,134
5,163
Aircraft Hardening
2,000
2,000
5,001
4,297
4,640
Airport Security
Technology Integration
2,485
2,708
2,285
2,457
2,084
TOTAL
44,225
51,690
50,147
54,400
50,325
12(...continued)
analysis for cargo and baggage screening. Its report is in preparation.

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Table 2. Bills to Improve Aviation Security Introduced Since September 11, 2001
(as of October 26, 2001)
Number
Title
Sponsor
Provisions Specifically Related to Screening
H.R. 2895
Aviation Security Enhancement Act of 2001
Lipinski
federalization, limit on carry-on baggage
H.R. 2898
Federal Airports Security Enhancement Act
Traficant
federalization
H.R. 2906
Emergency Aviation Security Act of 2001
Baker
H.R. 2913
Aviation Security Improvement Act of 2001
Quinn
federalization
H.R. 2951
Aviation Security Act
Ganske
federalization, screener training and employment
H.R. 2957
Secure Aviation Employment and Training Enhancement Act of 2001
Castle
H.R. 3029
Baggage Screening Act
Inslee
expanded screening
H.R. 3056
Flight Deck and Aircraft Integrity Enhancement Act of 2001
Traficant
H.R. 3064
Airline Security Act of 2001
Baca
passenger profiling
H.R. 3067
[to give hiring priority to workers who lost jobs as a result of attacks]
Harman
H.R. 3101
Aviation Security Technology Enhancement Act
Matheson
equipment
H.R. 3110
Transportation Security Enhancement Act of 2001
Oberstar
federalization, screener training and employment
H.R. 3150
Secure Transportation for America Act of 2001
Young
federalization, screener training and employment
H.R. 3165
Aviation Security Act, II
Ganske
federalization, training, equipment, research, reports
S. 1421
Emergency Aviation Security Act of 2001
Hutchison
S. 1429
Airport and Seaport Terrorism Prevention Act
Edwards
federalization, screener training, screening equipment
S. 1444
Federal Air Marshals and Safe Sky Act of 2001
McConnell
S. 1447
Aviation Security Act
Hollings
federalization, training, equipment, research, reports
S. 1461
Airline Passenger Safety Enhancement Act of 2001
Durbin
federalization
S. 1473
[to provide for enhancement of security at airports in the United States]
Johnson
federalization
S. 1515
[to provide for enhanced security with respect to aircraft]
Kohl
screening program requirements
S. 1544
[to give hiring priority to workers who lost jobs as a result of attacks]
Kennedy