"We were flying planes long before we understood flight." This isn't true. Sir George Cayley elucidated several aerodynamic principles significantly in advance

"We were flying planes long before we understood flight." This isn't true. Sir George Cayley elucidated several aerodynamic principles significantly in advance of the Wright Brothers first flights. The Wrights took advantage of this knowledge in designing their propellers and planes. We have since learned a lot more about how flight works, but the guiding principles of lift, drag, and thrust predate the mechanical engineering to realize a heavier than air aircraft.