Even within the framework of "reasonable expectation of privacy," the test outlined in Katz v. US leaves no room for the concept that an expectation will ever truly be "settled." To show a reasonable expectation of privacy, an one must demonstrate an individual, subjective expectation of privacy, and also that this expectation is something society would find reasonable.
So gee, does society find it reasonable to expect that you can walk through an airport without having your photo taken and analyzed by the government, and possibly stored in a database where it can be abused by internal or external actors? Viewed in the context of past behavior, perhaps not. Viewed in the context of a government that is suspicious of big tech surveillance even as it collects ever-more data on its citizens, and jurisdictions like the EU passing ever-tighter regulations like GDPR to safeguard privacy, then maybe society's expectations of privacy have shifted compared to where they were in the 2000s/2010s.
The US government is acting within well-established legal guardrails if they were to carry out the same tasks in a highly manual fashion. If it carries out the same tasks in an automated manner, the substantial legal issues remain exactly the same: there's a change in efficiency, an increase in data capture, and improved accessibility to authorized parties, but the fundamental act of capturing images, cross referencing them to a database of known persons, and logging movement activities remain basically unchanged. I don't see how you could argue that this harms the notion of privacy in itself any worse than it already was already being harmed, and I don't see how one could construct a sound legal argument that the introduction of automation itself somehow introduces additional damages.
We also don't really know where the resulting data is stored, or who will have access to it, or which people will abuse this information in the future, whether they are corrupt officials or third-parties who steal the stockpiled data, or what creative applications they will find for that data, or what harm the general public will ultimately suffer. These were good what-if questions on Slashdot in the 90s, but after decades of tech growth and abuse in the public and private sectors, these are now important ethical concerns that must be addressed in order to safely allow government security services to automate more and more of their jobs.
It's simply a bad faith argument to compare a detective watching a single individual to every single person in a large international airport, because one must have a causal justification for their actions while the second simply performs it's programming, endlessly.
If we're going to become endlessly surveilled and tracked, we as a society should at least has the smallest bit of dignity and complain about it. If we all let our privacy be eroded so tacitly, we go down like dogs.