Mr. Takemoto would not disclose how many agents were at the center or how many overall might be put in the air.

Air marshals first took to the skies in the 1970s. The current air marshals program, which has fallen into disuse in recent years, began in 1985 in response to the hijacking of a TWA flight. The revival of the program is the latest in a series of steps designed to plug holes in what critics call a porous security network. More changes might be coming.

Last week, four members of the U.S. House Subcommittee on Aviation said they would introduce legislation that would bring screeners at airport security checkpoints under federal control and place limits on carry-on baggage to make the screeners' jobs easier.

Two "rapid response" task forces created Sunday by Transportation Secretary Norman Mineta – to examine improving airport and aircraft security – will consider those and other options and make recommendations by Oct. 1.

Some industry officials said Monday that many of the proposed changes were not new and expressed frustration that it took an act of terror – the hijacking of four commercial jetliners – to give them legitimacy.

Patricia Friend, president of the Association of Flight Attendants and a member of the aircraft task force, said her association had asked the FAA for years to limit the size and number of carry-on bags.

"It would reduce the amount of baggage that comes through those checkpoints," she said. "We believe it would improve the efficiency of screeners. It would increase the chances that they would, in fact, identify items that should not be on board the aircraft."

The FAA has rejected the idea of a standardized carry-on policy, choosing to let airlines set their parameters. Given reports that the hijackers took control of the planes with knives and box-cutters, the task force is likely to revisit the issue, Mr. Takemoto said.

After last week's attacks, much attention has been focused on contract screeners at airport checkpoints. Some believe that this minimum-wage, high-turnover workforce should be brought under the auspices of the federal government to ensure that they are better trained.

Billie Vincent, the FAA's security chief from 1982 to 1986 and now a security consultant in suburban Washington, said that screeners should be made "quasi-law enforcement" officials, with salaries starting about $30,000 a year, several months of training at the FAA Academy in Oklahoma City and the chance to move to such agencies as the FBI after reaching a certain level of proficiency.

"Let's make them a truly professional force," Mr. Vincent said.

Not everyone, however, embraces the idea of federal screeners. "The last thing the federal government needs is 16,000 to 18,000 more employees," Rep. John Mica, R-Fla., said, adding that it might be better to transfer oversight of these workers from the airlines to the airports.

Pilots seem intent upon improving the integrity of the cockpit. John Mazor, spokesman for the 66,000-member Air Line Pilots Association, said, "The first order of business is to get a fortified cockpit door designed, built and installed."

Mr. Mazor said that new procedures also needed to be developed so that pilots can resist hijackers – perhaps with guns, perhaps with "nonlethal defensive weapons." He would not say what those weapons might be.

Although the airline industry has been criticized for its opposition to some security proposals – the one affecting carry-ons, for example – a spokesman for its main trade group pledged cooperation with what has become an urgent national reassessment. "We are open to any discussions," said Dick Doubrava, managing director of security for the Air Transport Association.

Mr. Doubrava also said, however, that "We need to target our efforts. The public is being extremely tolerant and extremely understanding. But is it going to stay that way?"

Mr. Mica agreed, saying, "We hop around with a knee-jerk reaction every time we have a crisis and spend a lot of money on yesterday's terrorist threat." After the midair explosion of TWA Flight 800 in 1996 ­ initially thought to have been caused by a bomb ­ the FAA purchased a half-billion dollars' worth of explosive-detection equipment, Mr. Mica said.

The machines, he said, are "sitting on the sidelines at airports, rarely used," and in any event would not have prevented the recent hijackings.