Fly, you're on candid camera

Thanks to the Christmas Day bomb attempt, airline passengers in all probability will soon face a choice: a "full body" scan that sees through clothes, a pat-down, or not flying. Privacy advocates reject the first two options as too intrusive. But if you want to fly, or have to fly, the law gives authorities the power to make intrusive searches to protect you, other passengers, flight crew and property.

A federal court ruled in 2007 that passengers voluntarily give up all rights to be free of searches without a court order once they enter the search area at an airport.

The sad fact is that the movement toward broad application of scanning technology is being accelerated in part by the incompetence of security services. The latest would-be terrorist was able to board a flight despite a number of red flags that should have alerted authorities.

Already Great Britain and Holland have announced plans to use full-body scans at airports. Newspapers here and abroad have headlined it the "Invasion of the Body Scanners." Certainly, there is an element of science fiction in the prospect.

Passengers already submit to magnetometers that scan for metallic objects that might be weapons. Carry-on bags are X-rayed. Checked baggage is tested for tell-tale chemical residue.

The body scanning machines similarly will focus on safety concerns -- objects hidden under clothing -- and not on the full detail of the human body. Individual privacy should be protected by allowing scanning personnel to see only body outlines, not faces or the individual being scanned. No images should be stored or reproducible. According to the Transportation Security Administration, such features are already installed on machines in use at U.S. airports.

Full scans and pat-downs will reduce, but not eliminate, the risk that someone might smuggle explosives aboard an aircraft. Another layer of security should be provided through the use of profiling techniques.

Profiling also attracts the objections of privacy and civil liberties advocates because of its association with law enforcement abuses. But profiling advocates make the point that the objective is to recognize behavior that might be a clue to danger, and that such profiling is race-neutral.

To be effective, profiling measures would have to be applied by all airport authorities. And it would have to be applied by personnel who are sufficiently competent to react to a demonstrable hazard.

If, as alleged, the Christmas Day bomber purchased a one-way ticket from Nigeria to Detroit with cash and traveled without baggage, that behavioral profile should have been a red flag. It should have instructed authorities to pull him aside at the airport for special scrutiny and not allow him to proceed without further search and investigation.

Any enhanced security measures the government adopts will face court challenge from the American Civil Liberties Union and allied groups seeking to narrow the scope of the government's search powers.

Such pressure has already caused the government to find ways to reduce invasions of individual privacy by body scanning technology. To that extent the privacy lobby has made a useful contribution. But Americans want to fly safely, and more intrusive searches appear to be an inevitable future cost of their travel.