What is the International Standard Atmosphere used for?

The International Standard Atmosphere (ISA) serves as a reference for performance calculations in aviation. It provides a model of how atmospheric conditions vary with altitude, standardized at specific temperature and pressure values. This model is crucial for engineers and pilots as it allows them to make accurate calculations related to aircraft performance, including lift, drag, fuel consumption, and engine efficiency. By using the ISA as a baseline, performance metrics can be consistently applied, ensuring that aircraft operate within their designed parameters regardless of varying real-world conditions.

The other choices do not accurately reflect the primary purpose of the ISA. While it might indirectly impact training or the development of operating procedures, those aspects are not its primary function. The ISA is fundamentally about establishing a consistent framework for evaluating how aircraft will perform under standardized atmospheric conditions.