The ones who would benefit from it being open sourced are the passengers and plots. Your excuse is mitigatiable, release it picewise, starting with the customer facing code to trusted outside groups.

Ultimately your argument applies to all life or death code, even code we put inside our bodies, which as you mentioned, is also highly specific and specalized.

Because the bar is higher there should be less review is a contradiction.

APT (often not a State) conversations are pointless where plausible deniability is ignored as a desirable property.