Concern about system interoperability and data privacy have grounded the Department of Homeland Security's prototype airline passenger-risk-assessment system. It was billed as a way of keeping terrorists off commercial airplanes.

Homeland Security secretary Tom Ridge announced the demise of the Computer Assisted Passenger Pre-Screening System (CAPPS II) during a flight from Boston to Washington. Ridge had been in Boston speaking about security precautions being taken for the upcoming Democratic National Convention. The department, however, says a CAPPS III might be proposed.

A department spokeswoman Thursday said she couldn't elaborate on technology issues that hindered CAPPS II, but she did say that the project would be redirected to take into account data privacy concerns. "Homeland Security is still highly committed to replacing the antiquated passenger pre-screening program already in place [known as CAPPS], which Transportation Security Administration inherited," she said. There is no yet timetable for the new project.

CAPPS II was being developed to use information that passengers submit when making reservations " name, date of birth, home address, and home phone number " to confirm a traveler's identity and assess that passenger's risk level. As planned, risk-level data would be deleted for most passengers once they reached their destinations. Data for high-risk travelers would be retained for an unspecified amount of time.

The department's goal in developing CAPPS was to protect airlines from terrorist attacks while also flagging violent criminals with outstanding federal or state arrest warrants. The original CAPPS program was administered by the airlines themselves under federal guidelines.

But CAPPS II was resisted by some from its inception. Privacy and civil-rights activists criticized the program's access to personal data and the absence of any way for travelers to challenge an unfavorable risk designation. The Senate Governmental Affairs Committee in February began investigating allegations that the Transportation Security Administration had compelled airlines to provide TSA contractors working on the project with sample passenger name data.

The airline industry itself wasn't opposed to having a way to "separate the good guys from the bad guys," says Doug Wills, VP of communications for the Air Transport Association, an airline trade organization. "That approach makes sense, but [CAPPS II] was derailed because the government couldn't figure out the privacy piece."

Earlier this year, Ridge signed off on changes to CAPPS II designed to address rising privacy concerns. Before activating CAPPS II, Ridge sought to have TSA thoroughly review the system to evaluate speed, accuracy, and efficiency. This would serve to reduce the number of passengers misidentified as threats to passenger or airline security. Ridge's revised plan also would have prevented commercial data providers from owning or retaining passenger name records and from using bank, credit, or medical records.

CAPPS II set a dangerous precedent by promising to give the government the power to fight terrorism by sifting Americans into trustworthy and not so trustworthy designations, says Jay Stanley, communications director of the ACLU Technology and Liberty Project. "The way to stop terrorism is through good physical security and reliable intelligence," he says. "It's not effective to sort through hundreds of millions of Americans using computer algorithms."

Although TSA claims it didn't have access to passenger name records, Department of Homeland Security Chief Privacy Officer Nuala O'Connor Kelly in April launched an investigation to determine if TSA violated the Privacy Act by not providing public notice of what type of information their screening systems would use and how individual passengers could find out if their data was included in the test systems.

The Governmental Affairs Committee in June found that at least eight airlines and airline reservation services handed passenger data over to contractors working to build prototype technology for CAPPS II.