But being known to the government is the closest to one, and the TSA already is experimenting with it. Its PreCheck program is designed to give expedited screening to travelers who tell TSA about themselves as frequent fliers at specific airlines. One million passengers have participated since it began testing in October 2011. TSA plans to expand it to 35 airports this year.
For $100, Customs and Border Protection has a similar program for foreign travelers called Global Entry, which also qualifies fliers for PreCheck.
The airlines say they could eliminate paper from ticketing if passengers provided information as they do for PreCheck, by linking an electronic ticket to a person's fingerprint or iris scan.
Iris scans, which measure the colored part of the eye, are gaining visibility worldwide. Schiphol Airport in Amsterdam began the Privium program in October 2001. It offers fliers with European passports a border passage of 10 to 15 seconds with iris scans.
In the USA, about 200,000 fliers have enrolled in the CLEAR program for expedited screening in Denver, Orlando and San Francisco since November 2010. Members, who answer TSA questions and provide either a fingerprint or iris scan, pay $179 a year to breeze past ID kiosks with a special card.
Caryn Seidman-Becker, CLEAR's chief executive, says the program brings "much-needed speed and predictability" to traveling.
SRI International of Menlo Park, Calif., developed two kinds of iris scanners for airports. One is a turnstile called N-Glance and the other is a portal called PassPort, which looks like a metal detector.
"Instead of using a card or a pass, you would simply glance at a spot on the turnstile and it would open the gate if you were qualified to go through," Mark Clifton, vice president of products and services, says of the prospects for airline passengers. "It's very fast."
Screening could also speed up. Peter Kant, executive vice president of Rapiscan, which makes full-body scanners, says several companies are developing machines fashioned like tunnels that allow travelers to walk through.
Rapiscan has a prototype that would let people keep moving, although it can't scan carry-on bags at the same time yet, Kant says.
"It's out of the lab, but it's still a prototype. It allows people to walk through without stopping or posing," Kant says. "You wouldn't have to be there doing all this unpacking and repacking."
As equipment is developed, the checkpoint ideally would require three tunnels for passengers. Each would be based on the potential threat that a passenger represents. Travelers who provide information like PreCheck would receive the least scrutiny. Unknown passengers or those with liquids would face the most sensitive tunnel.
Dunlap of IATA says initial studies show that breaking down lines into different security risks in programs such as PreCheck already speeds the lines 30%. Having three tunnels should speed the process more, he says. Passengers would be diverted for secondary screening, such as swabbing for explosives residue or pausing for a full-body screening, Dunlap says.