Something to understand here, it is exactly the same with the automotive industry. It is almost never about the actual safety, let me explain.
If you work as a safety engineer in a company like Boeing the name of the game is to not be responsible for the safety of a component at all. You always hide behind some kind of certifications then always ask a contractor to do it. The contractor might be scared too so will ask for a subcontractor and so on until someone is in an obscure juridiction or brave enough to just develop the software like almost anyone else but just with someone rubber-stamping the paperwork.
The safety engineer will have the paperwork so for them, it is safe! If there is an issue this is not them.
So for them Linux is absolutely out of the question, who wants to sign a paper for it?
Honestly just anti-foss rambling. Nothing is stopping them to make a custom hardened kernel with what they need. What they want is someone else to cater for them.
Well, NASA trusts Linux enough to send it to Mars. They build rockets, so it should be good enough for flying busses. Unless you don't trust your software engineers, but then having them build a custom microkernel OS instead sounds not much better.
I agree that a small, special purpose OS would probably be more suitable for safety-critical systems. On the other hand I highly doubt that the safety-culture is better at Boeing than in the Linux ecosystem.
You forget to take into account that every Boeing employee knows they are building systems that can kill people if things go wrong. Meanwhile on Linux a lot of bugs really don't matter that much, especially in -rc and otherwise non LTS versions.
Taking that into account their safety culture is much worse.
A bunch of bullshit so that Boeing can sell the shit they want to sell.
I'd be interested in hearing what they are using for safety-critical OS. Notice they said "software engineering" and not "OS", which makes me think they're running on Windows.