Air was a standalone app, but it wasn't clear why and they got feedback that this wasn't wanted. You can have the exact same GUIs and functionality integrated into the IDE and it's a pure functionality upgrade. For example, Air in IntelliJ/their other IDEs lets you do things like execute SQL queries on connected databases from the chat box and have the results be sent straight to the model.

There's a school of thought that says IDEs are history, their functionality is now worthless etc. But apparently lots of people don't think that.

I guess I'm one of those people too, because I tried the Air standalone app but it didn't gel for me for some reason. But I tried Air in IntelliJ and it immediately clicked. If models were always perfect and their work never benefited from reviews or changes, fine, you could argue the IDE is pointless. But it's been years and I've not yet found a model where that's true. You can slop for a while if the project isn't that important but for the stuff that matters, human intervention still changes the quality slope quite a lot.