As protesters and police clashed outside of the Phoenix Convention Center last month during President Donald Trump’s rally, everyone could hear the helicopters flying above.

But much higher in the air, something else was flying that not many knew was there: A Phoenix Police Department plane.

It’s part of a larger aerial surveillance program that many Arizona and federal law enforcement agencies use, and that most of us don’t really know about.

It turns out that Arizona law enforcement agencies use aircraft for everything from search and rescues to support for officers on the ground and to, of course, surveillance.

The Arizona Republic’s Jerod MacDonald-Evoy dug into this more in a recent project for the paper, and he found there are some serious privacy concerns that haven’t yet been addressed in this rapidly-advancing arena.