Updated

Security concerns have caused the government to suspend plans for an ambitious program to check every domestic airline passenger's name against government watch lists.

Transportation Security Administration chief Kip Hawley told the Senate Commerce Committee Thursday that he has directed that the program's information technology system "go through a comprehensive audit."

Hawley did not say whether any security flaws or breaches had been discovered.

"We don't believe any passenger information has been compromised," Amy von Walter, spokeswoman for TSA, told reporters.

The program called Secure Flight has been troubled from the start.

It is strongly opposed by civil libertarians who fear the program would grow into a massive domestic surveillance system in which the government tracks people whenever they travel.

Nearly four years and $200 million after the program was put into operation, Hawley said last month that the agency hadn't yet determined precisely how the it would work.

Government auditors gave the project failing grades — twice — and rebuked its authors for secretly obtaining personal information about airline passengers.

Currently, airlines check the names of passengers against watch lists that the government gives them. Under Secure Flight the government would take over from the airlines the task of checking names against watch lists.

The Sept. 11 commission later urged the administration to expedite the task because, it said, the watch lists currently used by airlines aren't complete.

But checking names against watch lists hasn't been as easy as it sounds, partly because airlines collect only limited information about passengers.

Also, the number of names on the watch lists increased into the tens of thousands since the Sept. 11 attacks. That problem has resulted in passengers from infants to Sen. Edward M. Kennedy being mistakenly told they couldn't fly because they have the same name as someone on the watch list.

The project has also drawn protests from privacy advocates and civil libertarians because its stated purpose has changed, often expanding.

Project managers once said that it would be used to track down violent criminals, and then backed down. They've also proposed using commercial data, such as that supplied by Choicepoint, to locate members of terrorist sleeper cells among people who buy airline tickets.