Basically, understanding airfoils. Back in the 1840s they put miniature steam engines in model planes and got them to fly. There were powered ground-effect plan

Basically, understanding airfoils. Back in the 1840s they put miniature steam engines in model planes and got them to fly. There were powered ground-effect planes in the 1800s that had more powerful engines than the Wright Flyer, but the Wrights were the first people to invent the wind tunnel, so they had a better understanding of lift-to-drag and control surface issues. They adapted the flow-pattern analysis tanks used by ship designers. As mcarmichael said https://youtu.be/EkpQAGQiv4Q?t=391 https://youtu.be/EkpQAGQiv4Q?t=391