You need brains to make paper planes. The work involves symmetry and also aerodynamics.
Now Mathspig recommends paper planes making as a Friday Maths Madness activity.
Put a waste paper bin on the front desk and every time students finish a problem or a set of problems they can write their name and answer(s) on a paper and fold it into a paper plane and aim it into the bin.
The most correct answers IN THE BIN wins a prize!!!!