This may be well known, but it wasn’t terribly obvious to me from Adobe’s documentation.

If you want to use the adobe AIR update framework including the UI in a pure AS3 AIR project, it looks like you need to start using the flex framework.Indeed, the documentation for “flash apps” recommends custom building an interface.

This is unnecessary – I picked out the applicationupdater_ui.swc from flex_sdk\frameworks\libs\air and accessed the ApplicationUpdaterUI class just as the documentation advised for a flex implementation and Lo – it’s all there, and it doesn’t include the whole of flex. It does add a few hundred kb, but it’s an installable AIR app, so that’s not such a big deal.