I heard recently of a patient that took some prescribed medication before her surgery, but instead of taking 5 mg as prescribed she ended up taking 5 grams, which induced a near fatal stroke. You could argue that better design could have prevented this from happening.

Edit: The mistake was between mg and ml, so the person drank 5ml of a 5X concentration drug. Either way a terrible, preventable result.

There was a famous airline accident where gallons of fuel was confused with liters. The fix (obvious in hindsight) was to standardize on gallons.

You're thinking of the Gimli Glider, https://en.m.wikipedia.org/wiki/Gimli_Glider

Boeing had just transitioned their FQIS from lbs to kgs (aircraft fuel is always weighed, volume changes with temperature). The flight crew hadn't had enough familiarisation and miscalculated.

All aircraft now calculate fuel usage in SI units.

> aircraft fuel is always weighed

Jet fuel is typically planned by weight. Avgas is typically planned by volume. In general aviation, both are typically priced and sold by volume.

> All aircraft now calculate fuel usage in SI units.

All 3 of my aircraft track/calculate fuel usage in imperial units. Likewise, everyone I know in US general aviation also still uses imperial units (lbs, lbs/hr, gallons, gal/hr).

I wish people would stop saying imperial when they mean US Customary!

An imperial gallon is about 4.5 litre while a US Customary gallon is about 3.8 litre.

Fair point. Thanks for the correction!

Fair points, I was speaking to commercial aviation.

Thanks for the correction.

mg ml vs mg g is roughly comparable for many liquid, so still roughly the same.

Missing the point. The doses by mass are specified in terms of (main) active substance, not the whole solution.