Although attempts at human flight go back centuries, George Cayley is recognized as the first person to analyze what technical necessities were required for flight. After investigating different models, Cayley's designs for fixed-wing devices led to the insight that flight required list lift, propulsion and control. Through the early nineteenth century, Cayley worked on various gliders, adding concave wings at slight angles and rudders. He recognized that his glider needed an engine, but was unsuccessful at building one. Without that component, his device only flew for a few hundred yards before crashing. Here, Sir Richard Branson pilots a replica of Cayley's flyer in 2003.