In practice all supersonic transports have used essentially the same shape for subsonic and supersonic flight, and a compromise in performance is chosen, often to the detriment of low speed flight. For example, Concorde had very high drag (a lift to drag ratio of about 4) at slow speed, but it travelled at high speed for most of the flight. Designers of Concorde spent 5000 hours optimizing the vehicle shape in wind tunnel tests to maximize the overall performance over the entire flightplan.