What if the pilot is depressed because his wife just died? What if the coffee cooker has been badly serviced and will start a fire? What if there's a tired ATC controller and we collide mid air with another plane? What if the engine has a slight imbalance, falls apart, and the parts hit some hydraulic line that immobilises the control surfaces etc.
I think it has to do with being a programmer, I see bugs all day and I can just imagine what can go wrong in an aircraft.
Also in the mix: A fear of heights and a fear of death.
What helped me: Statistics, realising that I am more likely to die sitting on my couch than sitting in a Boeing 757.. That I am relying on far less sophisticated drivers on the road to not mess up, and I am ok with it. That life is uncertain and that I can't live in in fear. And the fact that planes cannot just fall out of the sky, they are shaped in a certain way that ensures flight as long as there is wind hitting the front of the aircraft. And they make their own wind with their engines..
It just clicked eventually and now I'm even enjoying turbulence (as long as I don't spill hot coffee over my pants).. I also don't mind to crash and die, to be honest. After all, I am not Peter Thiel or Ray Kurzweil, so death is 100% certain for me. So why not die doing something I enjoy.
Of course the odds are I won't perish in an aircraft. At home on my sofa, now that's more likely..