In the not-so-distant future, airport security efforts might start the instant a traveler buys a ticket.
With a mouseclick, a reservation is locked in online, and a computer-mounted webcam transmits a snapshot of the traveler's face. The image serves not only as a credit-card signature, but also as a visual reference that can be used as an ID check at the airport.
A hypothetical example, but it could well become the first step in a system of preflight security that is growing significantly more rigorous. Flight-day precautions will likely include a gauntlet of facial scans, palm prints, explosive-chemical sniffers, and advanced X-ray machines.
By itself, a battery of detection devices will never remove all vulnerability to terrorism, experts say. And to be effective, screening devices must be supported by guards who can pick up on unusual behavior as well as run the equipment.
But such measures promise to throw important new barriers in the path of airline criminals - and these technologies are already being implemented, to some degree, at leading-edge airports.
Check-ins won't necessarily become more onerous for law-abiding fliers. In fact, many new systems can function quickly and unobtrusively, experts say.
This year, for example, a select group of Americans who frequently fly to London on British Airways or Virgin Atlantic will be enlisted to test a "look 'em in the eye" test intended to speed them onto airplanes even as it serves as a security check.
The Yanks will no longer have to fumble for little blue booklets or dog-eared birth certificates. They merely will look into a video camera. It will scan their irises - the colored portion of the human eye - and compare the images with maps stored in a database.
The test is also a foretaste of a growing security role for "biometric" imaging - by which computers track people using digital representations of their unique physical features such as palm prints, fingerprints, facial features, and eye structure. The data can then be compared to databases on criminal suspects.
"You're making an assessment of who is flying and what they are flying with. Those are the two fundamental questions you ask," says Terry Hawkins, who heads the international security division at Los Alamos National Laboratory in New Mexico. "You can ask those questions face to face, or you can use technology."
For all its promise, technology will only achieve its potential if the airport systems are linked to comprehensive and up-to-date law-enforcement databases.
Perhaps only a couple of the Sept. 11 hijackers, for example, would have raised any warning flags had they gone through biometric scans before boarding their flights.
In the aftermath of their attacks, law-enforcement officials and policymakers have been scrambling to close potential loopholes, and high-tech approaches have received heightened attention.
When the Aviation Security Act passed the Senate by a 100-0 vote last Thursday, for example, it included an amendment that would require the Federal Aviation Administration to establish a post that oversees research and development for security technologies.
Some airports have been using biometric technologies for years, according to the International Biometric Industry Association (IBIA). At Chicago's O'Hare Airport, for example, a digital fingerprint system, combined with "smart cards," identify employees, delivery trucks, and their cargo entering the airport's air-freight area. US Customs workers must use their fingerprints and a smart card to enter the airport's secure areas.
At San Francisco International Airport, employees swipe a card through a reader and have their hands scanned before they can enter restricted areas. United Airlines uses a similar system at the entrances to its operations areas and its preflight briefing building.
At the Charlotte/Douglas International Airport in North Carolina, US Airways has been using iris-scans to ensure that only flight crews and employees can enter restricted areas.
Aviation officials have long recognized the potential these types of technologies hold for improving security. Last year, the International Air Transport Association, based in Geneva, launched a program to encourage the use of biometric systems for faster, more-secure airports.
Yet biometric approaches are not the only ones planners have an eye on, analysts say. Some improvements may come from changes in airport design.
In Los Angeles, Mayor James Hahn last week unveiled a proposal to cut back a $12 billion expansion of Los Angeles International Airport and focus instead on tighter security. One idea: Build a structure several blocks from the airport that passengers would use to check luggage and clear security. Buses would take them to the main terminals.
Biometric technologies, for their part, carry a civil-liberties price, notes Paul Dempsey, a former lawyer with the US Civil Aeronautics Board now at the University of Denver. Screening needs to be done better and faster, "but it will require some surrender of privacy and some erosion of civil liberties."
Constitutionally, such infringement traditionally requires a "compelling" national interest. He says the Sept. 11 attacks qualify.
How might you check in for a flight at the "secure" US airport of the future?
Perhaps like this: On your travel day, you arrive an hour before flight time at an airport park-and-ride, blocks or perhaps a few miles from the terminal. You enter a building, swing your digitally encoded key fob past a detector on a kiosk. It registers your ID, while a camera records your face and compares it with an image recorded when you bought your ticket online. The detector provides you with baggage-claim ID.
After attaching the ID to your bags, you turn them over to airline agents and board a bus to the terminal. There, the bags are screened for weapons, nuclear material, explosives, or dangerous chemicals. Then each is sealed and loaded onto the plane.
You head for one of many kiosks in the lobby. Another wave of your key fob, verified by your image, handprint, fingerprint, or iris patterns, yields a boarding pass.
At the passenger-screening checkpoint, you bid any friends or relatives goodbye.
You and your carry-on bag are scrutinized by X-ray, metal, and chemical detectors. Security guards, now federal employees, check your boarding pass and eye a monitor as you pass through. They watch the screen for any illegal objects or substances. They also watch for an on-screen signal that your image has scored a "hit" on law-enforcement suspect lists - vast archives of facial images.
You head for your gate. When it's time to board, there's a final ID check by cameras and a palm scanner as you slip your boarding pass through a data recorder. The biometric "signatures" are compared with those taken when you first arrived. The gate attendant smiles and welcomes you aboard.