AirScope 1.3.1 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The application is categorized as Lifestyle Tools. We recommend checking the downloaded files with any free antivirus. This free Mac app is an intellectual property of Haversine Ltd.
From the developer:
AirScope is a plane plotter that retrieves aircraft positions and measurements from online sources and displays them on top of a world map in radar / ATC style. When flying online with VATSIM or IVAO, it's often useful to have an overview of who's in the air at any given moment or which ATC positions are currently filled and online. AirScope shows just that in a stylish universal interface for iOS and macOS devices.
You may want to check out more software for Mac, such as CmapLite, Spartan or gps2geX, which might be related to AirScope.