Windows Defender has a number of known issues that result in it sometimes falsly flagging files like FlightplanSetup.exe as Trojan:Win32/Wacatac.B!ml. Flightplan is NOT ransomware or a virus of any kind and IT IS SAFE to run FlightplanSetup.exe contrary to the Windows Defender warning. It may be necessary to turn off Windows defender to run FlightplanSetup.exe, but you should immediately turn protection back on after installing Flightplan. Windows Defender will not flag Flightplan itself as ransomware or a virus, it only flags the setup executable because it was downloaded from the internet.
Contact support@simflightplan.com if you have questions or concerns.