2.4 million people pass through TSA checkpoints every day. Now, the agency is stepping up its technology to get people where they’re going faster, but it will affect the way they are screened. 

The Transportation Security Administration is testing the use of facial recognition at 16 airports across the country, including Los Angeles, Boston and Atlanta. 

Travelers put their photo ID into a slot, then a camera takes a photo of them and compares it to the ID. The technology is checking to see if the images match. It’s also checking the validity of the identification provided. A TSA officer is also present to sign off on the screening.

“Basically what you’re doing is scanning the ID and we’re making sure the ID is a genuine ID, not a fake ID. Then we are matching your photo, your live face against the photo on the ID. You’re actually matching your own ID’s photo and making sure you are the same person you assert yourself to be,” TSA Identity Management Capabilities Manager Jason Lim said. 

The TSA says the pilot project is voluntary, but critics have raised concerns about questions of bias in facial recognition technology and possible repercussions for passengers who want to opt out. 

“We’ve seen this before where something that is optional becomes essentially mandatory,” Jeramie Scott said. Scott is the senior counsel at the Electronic Privacy Information Center in Washington, D.C.

“Opt out, particularly when you’re traveling through an airport, is not really voluntary. Most of the time you’re just trying to get through security as fast as you can to make your flight. It’s not the situation where you’re usually making a well-informed decision. And this is particularly the case where oftentimes TSA hasn’t really informed people that they can opt out,” Scott said. 

In February, five senators demanded that the TSA halt the program. In the letter to the agency they said the technology represents a risk to civil liberties and privacy rights. 

“It’s a snapshot in time. Now, once the photograph is taken and the match is made, your ID scan as well as your live photo is deleted upon match,” Lim said. 

The TSA says the goal of the pilot is to improve the accuracy of the identity verification without slowing down the speed at which passengers pass through checkpoints.