Downloading XAirports 4.5.3 for Mac from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this app available. This software for Mac OS X was originally produced by Udo Thiel. XAirports for Mac lies within Games, more precisely Tools. We recommend checking the downloaded files with any free antivirus.
From the developer:
XAirports is a utility app that allows owner's of the popular flight simulator "X-Plane" to easily set COM and NAV radio frequencies and autopilot parameters while flying. This avoids pausing the sim to look up, memorize, and enter frequency data, as well as to fiddle with virtual knobs.
You may want to check out more software for Mac, such as XAirport, which might be similar to XAirports.