The most recent designs in commercial airplanes have necessitated a change in the nature of airplane safety assessment. It used to be sufficient to examine each separate system to determine the safety of the airplane as a whole. This is no longer the case. Commercial airplanes have become highly integrated machines. New methods and tools must be employed to ensure the safety of new airplane designs. The companies responsible for the design of new airplanes have independently developed methods and tools to accomplish this. New standards have been written which bring these tools together and present them in a logical and usable form.