Well, I recently posted about some problems I had with a flight where the avionics software was borked, and I told a joke about safety critical software.
Life is Funner than Me.
Imagine, you are zimming along in your F-22 Raptor, with the big googly shades on, and feeling all kinda hot and horny flying along in your gravity support tights at Mach 2, heading for Japan, when suddenly. Nothing.
You crossed the date line and your avionics systems suddenly fail completely. I bet you feel all let down and kind of ass-hattish when you have to slowly circle a refuelling tanker that is trying to show you how to get to Hawaii.
Now, that West to East bug needs fixing, and fast, after all, aren't the emerging enemies in Asia and the Fucked-Up-iStans?
Wow. Way to go.
I do remember reading about this problem for not only the shuttle, but also the B-52, which is that the intended life-cycle of the machine goes beyond the availability of the parts that make it up. I mean, who wants to keep an Intel 8086 fab running for the joy of the US military. Taking the example of the B-52, which has a service life scheduled until 2040, giving it a total service life of 80+ years, this means extensive retrofitting.
It is worth noting that the Russian forces tended to have two of the most used weapons in use today, the AK47, still hot after all these years, and the hillman and city insurgent's favourite, the RPG. Simple, easier to copy, build and and repair, and asymmetrically destructive. The RPG costs a few hundred dollars, and the tank it destroys costs ten million.
Complexity and functionality are sometimes serious enemies.