> use feet worldwide, to be fair

Many CIS countries and China use metre flight levels[1] and kilometres per hour for indicated speed reporting. Additionally, the ICAO has recommended transiting to metre flight levels since 1979[2]. More additionally, the Airbus A300 had flight levels initially set up to be metric (obviously, since it was an effort spearheaded by the French), but to appeal to American airlines the Airbus consortium switched to feet. Although I am positive that Airbus engineers work exclusively in SI.

METARs worldwide except in North America use SI units for reporting weather.

[1]: https://en.wikipedia.org/wiki/Flight_level#Metre_flight_leve...

[2]: https://en.wikipedia.org/wiki/International_Civil_Aviation_O...