For quick airport check-in, just scan cellphone

First came the kiosk, a strange addition to airport terminals when Continental Airlines began offering it as a check-in option in 1995. It was followed by Web check-in, introduced by Alaska Airlines in 1999.

Now, with 80 percent of passengers using these self-service options, the next step is electronic boarding passes, which essentially turn the hand-held devices and mobile phones of travelers into their boarding passes.

At least half a dozen airlines in the United States currently allow customers to check in using their mobile devices, including American, Continental, Delta, Northwest, Southwest, and Alaska.

But so far, Continental is the only carrier in the United States to begin testing the electronic passes, allowing those travelers to pass through security and board the plane without handling a piece of paper. Their boarding pass is an image of an encrypted bar code displayed on the phone's screen, which can be scanned by gate agents and security personnel.

When using the other airlines' mobile check-in services, customers still have to print a boarding pass at an airport kiosk, though most carriers are eager to eliminate this step once the Transportation Security Administration gives its approval.

The agency has been working with Continental since December to test electronic boarding passes, which for now can be used only for nonstop domestic flights out of the Houston hub of Continental.

"We definitely see this as the wave of the future," said Andrea McCauley, a TSA spokeswoman. "It's something we are very enthusiastic about pursuing."

The mobile check-in may well be the first step in direct communications between airlines and passengers as they travel. Ultimately, Henry H. Harteveldt, a vice president with Forrester Research, said he expected airlines would use mobile messaging to communicate with passengers about on-board services, rebooking options, baggage pickup, and ticket purchases.

"It's clear that mobile is the gateway to how airlines will interact with their customers in the future for almost anything," he said.

The technology being tested by Continental uses a two-dimensional encrypted bar code, which is much tougher to copy than the one-dimensional bar code used by many airlines for boarding passes printed online. And that is a major reason the TSA is expected to embrace the technology.

"We've seen indications that terrorists might seek to use fake boarding passes to attempt to enter the security line," McCauley said. "When we scan the bar code, we know if it's been manipulated or if someone has tried to manipulate it."

With the electronic boarding passes, passengers still need to show photo identification when they pass through security, and that identification must match the information in the bar code on the phone.

The International Air Transport Association, which establishes global guidelines for the airline industry, expects that its 240 members will be using the bar code system extensively by 2011.