The area rule also holds true at speeds exceeding the speed of sound, but in this case, the body arrangement is in respect to the Mach line for the design speed. For example, consider that at Mach 1.3 the angle of the Mach cone formed off the body of the aircraft will be at about μ = arcsin(1/M) = 50.3° (where μ is the angle of the Mach cone, or simply Mach angle, and M is the Mach number). In this case the "perfect shape" is biased rearward; therefore, aircraft designed for high speed cruise usually have wings towards the rear.