Set the hovercraft down on a flat, smooth surface. Twist or pull the nozzle cap open without removing the balloon. As air flows out of the balloon, it'll start to hover! Try giving it a push and watch it slide around.
This activity is a great way for kids to experiment with friction. As long as the balloon is still filled with air, you can easily push the hovercraft across a smooth tabletop. But as soon as the air runs out, it quickly comes to a stop. The cushion of air reduces the friction between the CD and the tabletop, allowing your hovercraft to fly, just like the puck on an air hockey table.