This is the normal operation speed of an airplane. It’s the speed at which exceeding the limit load factor may cause permanent deformation of the aircraft structure. An aircraft normally cruises at about 85% of its top speed at any particular height. The cruise Velocity is when the aircraft maintains a constant airspeed. Commercial or passenger aircraft are usually designed for optimum performance at their cruise speed or VC. Airspeed limitations are shown on the airspeed indicator (ASI) by color coding and on placards or graphs in the aircraft. The red line on the ASI shows the airspeed limit beyond which structural damage could occur. This is called the never-exceed speed, or (Vne). A yellow arc indicates the speed range between maximum structural cruising speed (Vno) and the never-exceed speed (Vne).