Enlarge By Mandel Ngan, AFP/Getty Images Homeland Security Secretary Janet Napolitano USA TODAY OPINION Columns In addition to its own editorials, USA TODAY publishes a variety of opinions from outside writers. On political and policy matters, we publish opinions from across the political spectrum. Roughly half of our columns come from our Board of Contributors, a group whose interests range from education to religion to sports to the economy. Their charge is to chronicle American culture by telling the stories, large and small, that collectively make us what we are. We also publish weekly columns by Al Neuharth, USA TODAY's founder, and DeWayne Wickham, who writes primarily on matters of race but on other subjects as well. That leaves plenty of room for other views from across the nation by well-known and lesser-known names alike. * Contributors Board * How to submit a column Nearly a year after a thwarted terrorist attack on a Detroit-bound airliner last Christmas Day, the recent attempt by terrorists to conceal and ship explosive devices aboard aircraft bound for the United States reminds us that al-Qaeda and those inspired by its ideology are determined to strike our global aviation system and are constantly adapting their tactics for doing so. Our best defense against such threats remains a risk-based, layered security approach that utilizes a range of measures, both seen and unseen, including law enforcement, advanced technology, intelligence, watch-list checks and international collaboration. This layered approach to aviation security is only as strong as the partnerships upon which it is built. In addition to the more than 50,000 trained transportation security officers, transportation security inspectors, behavior detection officers and canine teams who are on the front lines guarding against threats to the system, we rely on law enforcement and intelligence agencies across the federal government. We require airlines and cargo carriers to carry out specific tasks such as the screening of cargo and passengers overseas. We work closely with local law enforcement officers in airports throughout the country. And we ask the American people to play an important part of our layered defense. We ask for cooperation, patience and a commitment to vigilance in the face of a determined enemy. As part of our layered approach, we have expedited the deployment of new Advanced Imaging Technology (AIT) units to help detect concealed metallic and non-metallic threats on passengers. These machines are now in use at airports nationwide, and the vast majority of travelers say they prefer this technology to alternative screening measures. AIT machines are safe, efficient, and protect passenger privacy. They have been independently evaluated by the Food and Drug Administration, the National Institute of Standards and Technology, and the Johns Hopkins University Applied Physics Laboratory, who have all affirmed their safety. And the weapons and other dangerous and prohibited items we've found during AIT screenings have illustrated their security value time and again. Rigorous privacy safeguards are also in place to protect the traveling public. All images generated by imaging technology are viewed in a walled-off location not visible to the public. The officer assisting the passenger never sees the image, and the officer viewing the image never interacts with the passenger. The imaging technology that we use cannot store, export, print or transmit images. If an anomaly is detected during screening with AIT, if an alarm occurs after a passenger goes through a walk-through metal detector, or if a passenger opts out of either of these screening methods, we use pat-downs to help detect hidden and dangerous items like the one we saw in the failed terrorist attack last Christmas Day. Pat-downs have long been one of the many security measures used by the U.S. and countries across the world to make air travel as secure as possible. They're conducted by same-gender officers, and all passengers have the right to request private screening and have a traveling companion present during the screening process. In the last two weeks we have also implemented a number of measures to strengthen our defenses against an attack using cargo shipments to the U.S. The deployment of this technology and the implementation of these measures represent the evolution of our national security architecture, an evolution driven by intelligence, risk and a commitment to be one step ahead of those who seek to do us harm. To fulfill the important role we ask of American travelers, and to be prepared at the security checkpoint this holiday season, be ready to remove everything from your pockets prior to screening. If you have a hidden medical device, bring it to the officer's attention before screening. We'll be better able to help expedite your screening that way. As always, we also ask the traveling public to be on the lookout for unattended bags or suspicious activity. Alert travelers have helped thwart plots and crimes in the past, and we encourage everyone to remain vigilant during a time when we know our enemies would like to strike. If you see something suspicious, report it to an airport security official or law enforcement. Each and every one of the security measures we implement serves an important goal: providing safe and efficient air travel for the millions of people who rely on our aviation system every day. We face a determined enemy. Our security depends on us being more determined and more creative to adapt to evolving threats. It relies upon a multi-layered approach that leverages the strengths of our international partners, the latest intelligence, and the patience and vigilance of the American traveling public. Janet Napolitano is secretary of the Department of Homeland Security. Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. 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