International Standard Atmosphere (ISA)

The International Standard Atmosphere (ISA) is a standardized model that represents average atmospheric conditions—such as temperature, pressure, and density—at various altitudes worldwide. It provides a common reference for engineers and pilots to ensure consistent calculations for aircraft performance, design, and navigation. In essence, ISA describes what the atmosphere is like at specific heights under typical conditions, helping aviation professionals predict how aircraft will behave during flight. While actual conditions vary with weather, the ISA serves as a baseline for safety, testing, and communication in aeronautics.