An option exists in the UNS-1 configuration file to disable the interaction between the UNS-1 FMS and the MSFS ATC system. The 'JF_146_UNS.ini' file is located in the following file directory: 

C:\Users\**USERNAME**\AppData\Local\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalState\packages\justflight-aircraft-146\work\JustFlight

Note: If this file does not exist, it will be created automatically once the fuel units are toggled between KG/LBS on the UNS-1 (can be changed via the FUEL > FUEL MENU page). 

In the 'JF_146_UNS.ini' file there is a "SynchFplWithFsATC" parameter. With this parameter set to 1 (default), the UNS-1 will integrate with the MSFS ATC system, and will automatically set the flight's destination based on the arrival airport set within the UNS-1. With this parameter set to 0, all integration between UNS-1 and MSFS ATC system will be disabled, providing the user with full control over the ATC system.

An option in MSFS titled "ATC ENFORCE FLIGHT PLAN" may also be used to disconnect the flight plan generated in the MSFS main menu and the UNS-1. Setting this option to OFF should disable this interaction. This option can be found in the following locations:

MSFS 2020:

MSFS Options > Assistance Options > User Experience 

MSFS 2024:

MSFS Settings > Assistances > Realism