In the U.S., the Transportation Security Administration (TSA) uses biometrics in two primary ways: to control employees' access to secure areas, and to verify the identities of passengers enrolled in PreCheck, the administration's program for low-risk travelers, allowing them faster screening.

But in various airports around the world, biometrics is being used in another capacity: to verify fliers' identities by scanning their faces, irises or fingerprints.

At the London Gatwick Airport, for instance, a trial took place in 2013 in which the airport processed 3,000 British Airways passengers without boarding passes, the Wall Street Journal reported. Instead, the travelers scanned their irises upon check-in, which then allowed security checkpoint cameras, and cameras at the boarding gates, to automatically recognize the passengers -- no boarding pass necessary.

The upside in trading security personnel for biometric security? For proponents, which include government and industry officials, it's that automation of airport security could free human screeners to focus more closely on detecting suspicious behavior and monitoring flagged travelers. These proponents also say that computers can be not only more thorough than humans, but also less error-prone.

Though in the U.S., the TSA says it doesn't have any current plans to use the technology to process travelers at the airport in the way London Gatwick Airport does, there are a few airports that have rolled out "exit portals" -- one-way pods that prevent travelers from backtracking into secure areas once they've exited the plane and keep outsiders from entering through the exits, NBC News reported.

Currently the portals simply provide a barrier between secure and nonsecure areas of the airport, but it technically is possible to equip them with biometric scanning technology, officials say.

But is replacing personnel with biometric technology the way to go? Opponents worry that security personnel will become so dependent on the technology that it will dull their senses.

"If you're sweating profusely, for example, the person checking your ID would notice," Arnold Barnett, an aviation-security expert and Massachusetts Institute of Technology professor, told the Wall Street Journal. "But that computer taking an iris scan wouldn't."

And if a human screener comes to rely solely on the technology, could such a thing be missed completely?