Jose writes:

That meters aren't used any more is a surprise to
me - the world is regressing.

Aviation is one of many examples of domains that are sufficiently
insulated from the world at large that they can easily use their own
units of measure without causing too much problem. Add that to the
enormous potential cost and risk of changing measurement units
worldwide, and it's easy to see why feet and knots have been retained.

Feet and knots are largely dimensionless in aviation. You don't
really have to know how long a foot is, or how fast a knot is. You
just have to plug the numbers in correctly when flying.

There is one universal domain in which old units are retained: time.
Since all present time is linked to all past time, it rapidly proved
impractical to decimalize time, and so the world still works with
hours, minutes, and seconds.

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