TSA says this is an optional program for travelers on domestic flights, while some foreign nationals may have to participate to be allowed on international flights.

Theoretically, there should be visible signage that notifies travelers they can proceed through airport security without doing the facial scan. In reality, not everyone will see the sign ― and it might not be in a language that a traveler understands.

I am one of the travelers who’s been agreeing to get my face scanned in airport security lines for years. But amid alarming reports of travelers experiencing bad treatment from border control officials, I’m reconsidering whether I should be submitting a face scan so easily to the U.S. government.