The latest measures to keep passengers safe in the skies.

More than six years after 9/11, nearly a third of American travelers described security as the biggest inconvenience of flying in a recent Associated Press survey. While airport security remains something of a hassle, progress is being made. The Transportation Security Administration (TSA) has introduced significant technological improvements as it screens some 730 million passengers and 657 million pieces of checked baggage each year.

The most common new device already in airports is an explosives-screening machine, which blasts passengers with gusts of air to detect chemical traces. Over the past three years, it’s been rolled out at close to 90 checkpoints at 36 U.S. airports, including Los Angeles International, Denver, and Miami, according to spokesman James Fotenos of the TSA. The SafeScout system, which can detect concealed weapons (including those made from unconventional materials, like ceramics and plastic), is also being tested. In use at Amsterdam’s Schiphol and, as of October 2007, Phoenix Sky Harbor International, the system is fast (the scan takes 1.5 seconds) and safe—it doesn’t use X-rays. Also on the horizon, new AT X-ray machines, which provide more- defined pictures of carry-on bags, will be deployed at 75 percent of the security lanes at major U.S. airports this year.

More controversial is the backscatter X-ray, which uses imaging technology to create pictures of travelers’ bodies during screening to help detect contraband. Field testing commenced in Phoenix in February 2007, and the TSA has plans to deploy additional machines in New York’s JFK and Los Angeles airports this year. Many passengers object to the idea of the latest technology being used to create revealing images of their bodies.

Still, if we have the ability to increase detection and safety while decreasing the inconvenience to the traveler, why haven’t these devices been introduced more broadly?The stalemate—between Congress, the airlines, passenger associations, and others—is due, at least in part, to the fact that airport security is about trade-offs. At what point is safety more important than privacy?Keeping confidential the wealth of data—addresses, phone numbers, credit card numbers, and dates of birth—that airlines collect is also an issue. Should federal agencies be able to access this information?

Future developments in security, however, may be as hard to predict as future threats. “We must use security measures that are unpredictable, agile, and adaptable,” TSA administrator Kip Hawley testified before Congress recently, “to put us one step ahead of evolving threats.”