hint at user registration for On Air service

website/documentation.py

@@ -837,8 +837,12 @@ def create_full() -> None:
         Thereby only the raw content and events need to be transmitted by your local app.
         This makes it blazing fast even if your app only has a poor internet connection (e.g. a mobile robot in the field).
 
-        Currently "On Air" is available as a tech preview and generates a random URL that is valid for 1 hour.
-        We will gradually improve stability and extend the service with password protection, custom URLs and more.
+        By setting `on_air=True` you will get a random URL which is valid for 1 hour.
+        If you sign-up at https://on-air.nicegui.io you get a token which could be used to identify your device: `ui.run(on_air='<your token>`).
+        This will give you a fixed URL and the possibility to protect remote access with a passphrase.
+
+        Currently On Air is available as a tech preview and can be used free of charge (for now).
+        We will gradually improve stability, introduce payment options and extend the service with multi-device management, remote terminal access and more.
         Please let us know your feedback on [GitHub](https://github.com/zauberzeug/nicegui/discussions),
         [Reddit](https://www.reddit.com/r/nicegui/), or [Discord](https://discord.gg/TEpFeAaF4f).