Not sure about npc's with jetpacks but my own sims if they have one in inventory will 'fly around' if idle, I don't know if just flying around causes it though so much as landing when teleporting somewhere, I've not seen a sim crash head first just flying around, only when arriving at a new place after the 'fly here' interaction, which you do have to tell them to do, it's the same as 'go here'.
But my flying around sim was high level advanced tech, perhaps you can crash at low level, either way just flying about is autonomous.