within carry-on items. Security equipment included transmission x-ray systems for carry-on bags and walk-through metal detectors for passengers. However, with this tragic event, the focus immediately turned to technologies capable of also interdicting explosives devices in carry-on and checked bags. Since the introduction in December 1994 of the first certified explosive detection systems (EDSs) for checked luggage, a technology based on computed x-ray tomography, explosive threat detection has significantly improved. Furthermore, the development and insertion of threat image projection capability into security systems such as those used for scanning passenger carry-on bags have also served to improve screener performance and awareness.

On November 19, 2001, President George W. Bush signed into law the Aviation and Transportation Security Act (ATSA) (Public Law No. 107-071), which mandated the federalization of passenger and baggage screening at more than 440 commercial airports in the United States by November 19, 2002, and the EDS screening of all checked baggage. On March 1, 2003, the Transportation Security Administration (TSA) was transferred from the Department of Transportation to the newly created Department of Homeland Security, as required by the Homeland Security Act of 2002 (Public Law No. 107-296). Virtually all aviation security responsibilities are assigned to the TSA. These responsibilities include conducting passenger and baggage screening and overseeing security measures for airports, commercial aircraft, air cargo, and general aviation. The TSA programs dealing with these matters are intended to form a layered system that maximizes the security of passengers, aircraft, and other elements of the aviation infrastructure.

The TSA has undertaken several programs to measure and improve the performance of passenger screeners in the detection of threat objects. In March 2004, the General Accounting Office (now the Government Accountability Office) completed a study of the performance of the passenger-screening system that identified numerous performance deficiencies, such as inadequate staffing and poor supervision of screeners. These deficiencies in performance were the result of a lack of skills and knowledge, low motivation, an ineffective work environment, and wrong or missing incentives. The TSA is taking steps to remedy these deficiencies, and although it is making progress in its checked-baggage screening operations, it continues to face technical, operational, and funding challenges in accomplishing the EDS screening of all checked and carry-on baggage as mandated by ATSA.3

The 9/11 Commission Report,4 issued in 2004, recommended that the Transportation Security Administration and the Congress improve the way screeners look for explosives at airports. “As a start, each individual selected for special screening should be screened for explosives.” Former Navy Secretary John Lehman, a member of that commission, told the House Aviation Subcommittee that the prospect of suicide bombers boarding U.S. aircraft is “a very real threat.” He said that it is more likely now


U.S. Government Accountability Office. 2004. Aviation Security: Improvement Still Needed in Federal Aviation Security Efforts. GAO-04-592T. Washington, D.C. Available at http://www.gao.gov/cgi-bin/getrpt?GAO-04-592T. Accessed June 25, 2006.


Available at http://www.9-11commission.gov/report/index.htm. Accessed June 25, 2006.

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