Aerospace and Defense engineering in the U.S. is almost exclusively in the standard system (imperial outside the U.S). If you want to know why we STILL have no

Aerospace and Defense engineering in the U.S. is almost exclusively in the standard system (imperial outside the U.S). If you want to know why we STILL have not moved to metric, compare the cost of replacing manufacturing assets calibrated, designed, and manipulated using standard units with training an engineer to use standard units and convert to metric when necessary. Fun fact: U.S. standard units are defined precisely in terms of metric units, and are often different from their British cousins.