Instead of actually saying that somthing is in the air in the properties instead make make the model higher into the air, so basicly it thinks its a ground unit but actually it is in the air.
The problems with this is that the green circle is on the floor, ground units with melee attacks can shoot it and it can not hover over a building or move over anothert building, neither can it go anywhere a air unit can go.
Another way might be to set the worker as being an air unit?? I dont know if it works but try it.
Hope this helps!