Gravity pulls down on airplanes and birds. That means that flying things all rely on other forces that are stronger than gravity to keep them up. Sometimes air can provide the force to overcome gravity. Take the beach ball off the blower and hold it above the floor as high as you can. Hold the ball above the blower and drop it.
Gravity pulls down on a roof, helping to keep it on the house.
Aim the air under the edge of the roof. Now try blowing the air across the top of the roof. Turn on the fan and experiment with the wing. Now tilt the wing so that the rounded edge is aiming down. Have the class, one student at a time, experiment with lifting a 500 lb. weight using the lever.