This is kind of a silly strawman in some ways, simply because all software - including the code helping fly jumbo jets, steer oil tankers or run MRI machines -

This is kind of a silly strawman in some ways, simply because all software - including the code helping fly jumbo jets, steer oil tankers or run MRI machines - is written by fallible humans, and is generally considered safe only because of QA testing, rather than code analysis. There are some rare instances of insanely complex code having every line thoroughly vetted like those in NASA projects, but pretty much everything else out there is simply "good enough" until a flaw is (inevitability) found and fixed. The decision trees generated by AI will be no different. Until, I guess, an AI can perform the analysis of the code of another AI... cue Inception music.