The Balitmore police has been using Persistent Surveillance Systems' technology since January 2016
Since January this year, a private company has been working alongside the Baltimore Police Department to conduct widespread aerial surveillance and help solve crimes including shootings, murders and hit-and-runs.
However, in a case that has piqued the interest of civil-rights groups such as the ACLU, the existence of the spy plane programme, which is managed by Ohio-based Persistent Surveillance Systems, has remained under-the-radar and highly secretive.
As revealed by Bloomberg, the private surveillance firm offers local Baltimore police support from the sky, and is able to use small Cessna planes equipped with monitoring technology to scan roughly 30-square miles of the city at a time.
To date, the police has not acknowledged the programme even exists.
The in-depth investigation into the use of these privately-funded planes showed how the police used Persistent Surveillance Systems to track members of the public who were protesting during the trial of the police officers charged in the death of Freddie Gray.