Make your own! Here's what you need:
a balloon
a gallon ziplock bag
a straw
string
tape
Step 1: Tie one end of the string to a chair.
Step 2: Slide straw onto the string.
Step 3: Tie the other side of the string to another chair.
Step 4: Tape ziplock to the straw.
Step 5: Insert balloon into the bag.
Step 6: Blow up balloon.
Step 7: Let go and watch it fly!
We just finished our Air unit with this very fun experiment - try it at home!