Biometrics are transforming the way we travel. The technology, which identifies travelers using unique physical traits like fingerprints and faces, is becoming more common at airports in the United States. As a result, time-consuming rituals that once required repeated ID checks — such as bag dropping, security screening and boarding — are getting easier and faster.

Some experts believe that this will be the year that biometric use, primarily facial recognition, becomes standard at many airports. The technology offers several advantages: enhanced security, quicker processing of passengers and a more convenient airport experience. It also raises concerns about privacy, ethics and the possibility of broader surveillance.

In today’s newsletter, I’ll explain how biometrics are already altering many travelers’ airport experiences, and how critics are pushing back.

Change is here

T.S.A. checkpoints at dozens of airports across the country, from Denver to Miami, look different than they did only a few years ago.

The agency is using technology that takes a photo of a traveler and swiftly matches it to a scan of their ID. This process will expand to around 400 more airports in the coming years, though it remains optional; travelers can still go through security the old-fashioned way if they prefer.

The T.S.A. has also developed programs with some airlines to enable PreCheck travelers, who are approved for expedited screenings at more than 200 airports, to check bags and even pass through security checkpoints by just showing their faces, no ID scan required. Airlines say these changes can save substantial time and make a noticeable difference in moving passengers through the airport.