> Where in the world can you self-certify anything?

In the US. Self-certification is pervasive in the aviation industry. For ex., an A&P self-certifies her own work. A pilot self-certifies night landing and instrument currency.

German car manufacturers self-certify the CO2 exhausts.

TEPCO certifies their Japanese nuclear plants.

Works great, doesn't it?

It was NOx, and they didn't self certify, they cheated the tests.

Car companies operate their own testing units at their factories. I don’t see how this is different from self certification.

Ex: “Today in Tokyo, Nissan joined the increasing list of automakers who have admitted to falsifying emissions and/or fuel economy figures. The company said it had uncovered falsified data from car exhaust emissions tests at most of its plants based in Japan.” https://www.forbes.com/sites/peterlyon/2018/07/09/nissan-adm...

Trust but verify is common worldwide for this stuff. Otherwise governments would need to install and operate a lot of equipment at every factory worldwide.

True, but an entity that goes so far as to cheat on tests is hardly likely to honestly self-certify - it is further evidence that some non-trivial form of verification is necessary.

I am not, however, going to take any position on whether Boeing has done anything wrong until the accident analysis is complete.