Boats Before Airplanes It may not come as any great surprise that humans have been getting around on the water using boats for thousands of years. Airplanes are a relatively new innovation that was inspired by watching birds cover great distances in very little time. Thanks to Archimedes principle (circa 246 BC), boats displace a volume of water equal in weight to the weight of the boat. This allows watercraft constructed of various materials (including wood, aluminum, steel, cement, and lead) to float and maintain their stability. Many wonder how airplanes stay aloft just as birds soar above a ridge full of updrafts. Airplanes are designed with a fuselage that carries passengers (or cargo), wings that generate lift, and appendages that provide control. The lift force must be at least as large as the weight force in order to maintain or increase the altitude. This is possible because of a principle called the Kutta condition. The formal definition is that the velocities leaving the t