For months, homeland security officials have privately debated how to blunt criticism of their planned aviation screening system that passengers and airlines complained was overly intrusive.

Yesterday, officials announced a friendlier version with a new name, "Secure Flight," and a new slogan, "Preserving our freedoms." But the system still will rely on key elements of the earlier, controversial program.

In a telephone press conference, David M. Stone, the administrator of the Transportation Security Administration, said that in tests this fall the system will still use automated analysis of passenger records provided by the airlines. It will also continue to rely on commercial data services to verify identities and match passengers against databases of suspected terrorists.

Stone said the new pre-screening system is different from its predecessor because it will not use computer models known as algorithms to assess individuals for risk. He also said it will not scan for wanted violent criminals, a function that senior homeland security officials added last summer over the objections of the program's designers.

In response to questions about the lingering similarities, Stone said that Secure Flight was entirely new. "There's a huge difference between the two," he said, adding: "This is a very intense focus on known or suspected terrorists."

Yesterday's announcement was part of an effort by homeland security officials to come up with a way to implement a viable passenger pre-screening system. The government created its first computer-assisted passenger pre-screening system (CAPPS) in the 1990s to search for hijackers. After the terrorists attacks in 2001, it began work on a second generation of the program, a vast, data-driven system known as CAPPS II, which has now evolved into Secure Flight.

The project has cost the government close to $100 million and has been repeatedly delayed by technical and policy questions. It also has been criticized for being overly secretive and intrusive.

Two years ago, senior government officials described CAPPS II as the single most important component of the nation's aviation security. As recently as last month, Deputy Secretary of Homeland Security James M. Loy said the CAPPS II program "remains, in my mind, one of the most important tools in the counterterrorism arsenal."

People close to the program said recently that Bush administration officials made it clear this summer that they were worried that the privacy questions sparked by the system could have a political impact during the presidential campaign. Security officials have postponed both testing and implementation of the system until after the election.

To prepare for Secure Flight testing in November, the Homeland Security Department will obtain "historic" passenger name records from the airlines, each of which contains more than two dozen pieces of information. Those records will be analyzed to find details that will help officials match with certainty a passenger name against terrorist watch lists. That's in part to minimize the misidentification of innocent travelers because their names are similar to those on the watch lists.

The airline records also will be used to test identities against commercial data systems managed by companies such as Acxiom Corp., ChoicePoint Inc. and LexisNexis Group, which maintain billions of records about virtually every adult in the United States. If the tests show that the commercial services improve security in a meaningful way, Stone said, the services will be used as part of Secure Flight in 2005.

"The CAPPS II, as we defined it, is no more," Stone said, adding that Secure Flight will be an "improved passenger pre-screening program."

David M. Stone of the TSA said there is a "huge difference" between the new system and its controversial predecessor, CAPPS II.