Under the system, called "Secure Flight," the Transportation Security Administration will screen for possible terrorists by comparing passenger data with names on two government lists. The "no-fly" list comprises known or suspected terrorists, while a "watch" list names people who should face tighter scrutiny before boarding planes.
The TSA order issued Friday gives 72 airlines until Nov. 23 to turn over computerized data for passengers who traveled on domestic flights during June.
The data — known as passenger name records, or PNR — can include credit card numbers, travel itineraries, addresses, telephone numbers and meal requests. The latter can indicate a passenger's religion or ethnicity.
Barry Steinhardt, an American Civil Liberties Union lawyer, said a major problem is the lists include the names of many people who are not security risks.
Among those subjected to extra scrutiny in recent months was Sen. Edward M. Kennedy), D-Mass. The singer formerly known as Cat Stevens, now Yusuf Islam, is trying to get off the no-fly list after he was removed from a London-to-Washington flight because the list said he had links to terrorists.
The lists are "a hodgepodge of information, accurate and inaccurate," Steinhardt said. "They're the basement of the program, and the floor is rotten."
The government has sought to improve its process for checking passengers since the Sept. 11, 2001, hijackers exposed holes. The government's first attempt was scuttled because of fears the government would have access to too much personal information.
The TSA says Secure Flight differs from the previous plan because it does not compare personal data with commercial databases. The agency said, however, it will test the passenger information "on a very limited basis" against commercial data.
Under the current system, the government shares parts of the watchlists with airlines, which are responsible for making sure suspected terrorists don't get on planes. But the airlines don't have access to everyone who's considered a threat to aviation because some of the names of known or suspected terrorists are classified.
People within the commercial aviation industry say there are more than 100,000 names on the lists.
Under Secure Flight, the government would take responsibility for checking passengers. That was among recommendations of the commission that investigated the Sept. 11 attacks.
An airline industry representative said the carriers support the government's goals but remain wary of privacy concerns.
"U.S. airlines have long-standing concerns that center on privacy and operational issues," said James May, president of the Air Transport Association, which represents major airlines. "We hope many of the issues will be successfully addressed during the test phase of Secure Flight."
About 500 people formally commented on the Secure Flight plan this fall. Almost all opposed it, saying it would allow the government to monitor where people go and deprive them of the right to travel without telling them why.
In issuing the order, the TSA didn't resolve another key concern for privacy advocates: redress. There still is no formal way for people mistakenly identified as terrorists, or who have the same name as a suspected terrorist, to get off the lists.
"They've done absolutely nothing to tell us what they really intend on doing," said Bill Scannell, a privacy advocate who manages the www.unsecureflight.com Web site. "Their attitude seems to be, `Trust us.'"
The TSA said it would set up a passenger advocate's office with clear policies and procedures.
On the Net:
Transportation Security Administration: http://www.tsa.gov