A folded paper airplane glides, banks and loops through a softly lit room, leaving a faint dotted flight trail. Its curved path comes from combining two things: a steady forward glide (lift roughly balancing gravity) and a slow left-right turning motion, which is what causes the wings to bank into the turn like a real glider. The looping rise-and-fall you see is an oscillation layered on top of that glide path, similar to how a thrown paper plane porpoises up and down as it slowly bleeds off energy.