[mh-]

You can forget to carry a 1 in metric, too.

[rvnx]

It won't save everything will will reduce at least two possibles routes of mistake (wrong unit, or imprecise conversion).

OP wrote "km miles", which would create an incident.

SpaceX uses metric system for that exact reason, because in the past, on Mars, accident happened because of imperial measures.

[Retric]

Yep, the point of saying “km miles” was the hypothetical uncertainty around units even for European airlines who use metric internationally. However, even within metric might be some question around units.