Big Brother is watching you at airports—and even Customs and Border Protection thinks it could be a bad idea.

If you go through Dulles in Washington, Houston’s George Bush and William P. Hobby airports, Chicago O’Hare, and McCarren in Las Vegas, as of 2016 you’ve been undergoing biometric screening. And more airports are on the way, with large-scale expansion of the program expected in 2018.

The screening program works by taking your picture and cross-referencing it to a database of passport and visa pictures of the passengers expected to be on flights. Customs and Border Protection only keeps the photos on file for 14 days, but because the program works by shared communication between CBP and the airline, the airliness have access to your picture, as well—and they are free to keep photos and biometric information on file as needed for business purposes. The biographical information itself is kept by CBP for 15 years for US citizens and 75 years for foreign travelers.

The problem is that CBP acknowledges that the information could potentially be used for other purposes than just airport screening.

“There is a risk that approved partners will use biometric images collected under the [service] for a purpose other than identity verification,” CBP said in a statement in June. Because it’s a partner program, there’s “a risk that commercial air carriers will use the photographs for purposes beyond departure verification,” the statement said, because “commercial air carriers are not collecting photographs on CBP’s behalf or under CBP authorities.”