How to open AirPane

1. Download AirPane.dmg from this site, open it and drag AirPane into Applications.
2. Open AirPane. macOS says it could not verify AirPane is free of malware, because AirPane isn't notarized by Apple yet. Click Done.
3. Open System Settings › Privacy & Security, scroll down to the Security section, click Open Anyway next to AirPane, and confirm with your password. You only do this once.

From Terminal instead:

This is the free beta: everything works while it lasts. If you have a licence key, it goes in Settings › Advanced › Licence.