In this activity, learners explore the properties of paper by constructing and modifying paper airplanes. This guide includes instructions for building a "Nakamura lock" plane, which may be new to learners more familiar with the simple dart paper airplane. Learners trim, or adjust the plane for flight, with the goal of having the plane glide smoothly and gently to the ground, either flying straight or in a gradual curve. Use this activity to help learners explore properties of paper and motion, including kinetic energy, permeability, thrust, lift, and center of gravity.