WASHINGTON — Despite stiff resistance from airlines and privacy advocates, the U.S. government plans to push ahead this year with a vast computerized system to probe the backgrounds of all passengers boarding flights in the United States.

The government will compel airlines and airline reservations companies to hand over all passenger records for scrutiny by U.S. officials. The order could be issued as soon as next month. Under the system, all travelers passing through a U.S. airport will be scored with a number and a color that ranks their perceived threat to the aircraft.

Another program will be introduced this year that seeks to speed frequent fliers through security lines in exchange for volunteering personal information to the government.

Privacy advocates say they are most concerned about CAPPS 2, or the second version of the Computer Assisted Passenger PreScreening Program. The Transportation Security Association believes the current screening system is based on old assumptions about terrorists, flagging passengers, for instance, who paid with cash or bought one-way tickets.

TSA said the new computerized system will provide a more thorough approach to screening passengers. It will collect travelers’ full name, home address and telephone number, date of birth and travel itinerary. The information will be fed into large databases, such as Lexis-Nexis and Acxiom, that tap public records and commercial computer banks to verify that passengers are who they say they are. Once a passenger is identified, the CAPPS 2 system will compare that traveler against wanted criminals and suspected terrorists contained in other databases.

The two-step process will result in a numerical and color score for each passenger. A "red" rating means a passenger will be prohibited from boarding. "Yellow" indicates a passenger will receive additional scrutiny at the checkpoint and a "green" rating paves the way for a standard trip through security.

Although it is unclear how many passengers will fit into each category, TSA said its best estimation is that 5 percent of the traveling public will be flagged yellow or red, compared with an estimated 15 percent of passengers who are flagged under the current CAPPS.

The U.S. government has not said how long it will keep data on air travelers. Information on most passengers screened by CAPPS 2 can be held only for "a matter of days," said Nuala O’Connor Kelly, the chief privacy officer at Homeland Security.

The government’s system to prove the backgrounds of all passengers boarding flights in the United States will distinguish passengers by color: