You can start testing it yourself. The only code I know of is a command called "nogravity". Place the following script in the main AI. However, the npc doesn't automatically float upwards. Where ever you place him above the ground is where he will remain. There was some script some time ago that you could at least make the player move through the air but I'm not sure where that is. Also, I'm not sure if the npc's will be able to at least "walk" through the air or fly through the air in perfect zero G conditions. So what you are looking for may not be possible.
;Artificial Intelligence Script
;Header
desc =
;Triggers
:state=0:nogravity,state=1
:state=1:none
;End of Script
