How can I make an AI agent randomly fly around in space?

All the tutorials I could find are for pathfinding. Does anyone have a good one for 3D direction random roaming AI?
I set the X/Y/Z rotations, and checked the “can fly” for the nav agent (I’ve never actually seen any example that used it, what is it even for), but the AI doesn’t actually turn in those directions, and it falls down directly to the ground.
Any advice?