I have a character script that uses the air material to create shadows around it. The air material before wasn’t like any other material because it’s still invisible with 0 transparency but leaves the shadow of the part.
This doesn’t seem like a bug, just undefined behavior. It’s not very obvious, but, the Air material is only really meant for use with Terrain, and nothing else. That’s why it doesn’t show up for parts in the properties panel.
This was an unintentional behavior, so this shouldn’t be considered a bug. You should instead provide a feature request for a new material with this effect and use this as an example for a use case.