Some U.S. companies are developing systems to cut down the time airline passengers spend going through airport security. One new system would use old technology to tag passengers who could be considered a threat.

The goal is to build a system that screens every passenger who purchases a plane ticket before the person arrives at the airport. That way, any passenger identified as a potential threat could be taken aside at the airport, reducing lines at security checkpoints.

The technology needed to create such a network has been around for 10 to 15 years. Internet security and privacy consultant Richard Smith says companies are building systems run by very smart computers that use something called neural networks.

"Neural networks are ... it is a technology that tries to decipher patterns by previous activity. So you take a look at say, what known terrorists did, and then you see if someone else is going through those same activities," he said.

An example of abnormal activity would be if an address did not match a name, or if a name did not match a phone number. Richard Smith says the security has been used for a long time to detect other types of illegal activity.

"Now where this technology comes from today, it is actually used for combating credit card fraud. When a credit card gets stolen, it tends to get used in certain ways and certain kinds of purchases, so they use neural networks to determine the fraud patterns. And then they look for other credit cards being used in the same way," Mr. Smith said.

Security Consultant Joe Del Balzo says that just like there is a set of rules the neural networks use to catch credit card fraud patterns, there is a set of rules the new aviation security system would check each passenger by.

"There are 26 specific rules that the computer makes an assessment against, and determines a risk associated with that passenger. If you violate all 26 rules, you wind up being a high-risk passenger," he said.

He says the computer would rate all passengers with risk levels. Anyone considered a high risk would be taken aside and checked thoroughly at the airport. But he says people who are determined to be low risks would be able to avoid going through heavy security and long lines.

"Technology allows us to cull down to two, three-percent of the people that we need to pay attention to. It allows us to decide how to deploy limited security resources at a given airport," Mr. Del Balzo said.

Critics of such a system say it would be an invasion of privacy. Joe Del Balzo says the technology would only check publicly available information.