The watchdog also pointed out uncertainty about help from airlines, such as requiring them buy the cameras needed for taking passengers' photos. That represents a "significant point failure" for the face scanning system, the Inspector General said. As a result, the oversight body warned that Homeland Security might not make its target of having the face scanning system completely ready for use in the top 20 US airports by 2021.

That's still roughly three years out, and CBP wasn't convinced it would fall short. However, it did promise to create an "internal contingency plan" if it couldn't get help from airports and carriers. Don't be surprised if there are delays, or if there are significant changes in strategy to reach that 2021 goal.