The objective of this paper is to inform the aircraft flotation analyst of the currently acceptable methods of calculating flotation, to show how those methods relate to each other, and to discuss the flotation classification (ACN-PCM) that is on the threshold of acceptance.Worldwide, some sixteen methods of calculating flotation are currently in use. This creates confusion for the procuring agencies, aircraft companies, and airport authorities. The International Civil Aviation Organization has addressed this problem by advocating universal use of the LCG method, later the LCG method, and now the ACN-PCN classification. However, many analyses are still being made using methods such as PCA and 5-77-1.This paper defines flotation terminology and flotation parameters such as single wheel load, radius of relative stiffness, surface type, subgrade and surface fatigue. It summarizes the analysis methods (both old and new) and compares the LCG and LCG methods. Recommended analysis methods are listed, categorizing them for commercial and military usage, by military service to be satisfied, and by the type of runway. Obsolete methods are listed, with appropriate discussion of superseding documents. Finally, the correct usage and limitations of flotation analysis are reviewed-emphasizing that the calculated values should be considered as relative numbers rather than absolute values.