An ornithoptor is a large flying machine. It is shaped much like a bat's wings and could be used to let humans fly. To make this invention, Leonardo da Vinci did many experiments and detailed observations on birds. He took down everything in his journals, trying to find the secret to flying. By the time he finished, da Vinci had over 35,000 words and 500 sketches on the flight of birds. Then, he published his works together in a codex called "Codex on the Flight of Birds." But even after all of that work, da Vinci discovered that bat wings were better for the design because they glide better and can carry heavier objects. The ornithopter has many of the traits used to build planes, and if da Vinci's journals had been readable at the time, we could've had airplanes a lot sooner!