Ah, yes. Thanks for the reminder. Encroaching senility, I'm afraid!

Now that I recall, I made that comment after only running a few missions, but I now believe that it was probably just a coincidence. However, it may make sense to pay closer attention to that, just in case. If I may make a guess, my sense is that the sim performs a "dice roll" for failures on an ordinal basis (AC1, AC2, AC3, etc.) and if it gets a "hit" the sim stops "rolling" and waits for the next roll opportunity. As a consequence, AC1 is more likely to have a failure than AC2, AC2 more than AC3, and so on, but at least in theory, a failure can occur to any aircraft in the flight. Another question is whether the sim performs this dice roll for the whole flight, or one aircraft at a time.

I think your idea of possibly increasing the likelihood of non-cumulative "lesser" failures is a good one. Right now, there is roughly a 50-50 chance that your engine failure will be a catastrophic and possibly fatal failure. In real life, while such catastrophes certainly did occur, the vast majority of engine failures were relatively minor. I know I don't like it when my aircraft blows up!

I figured you were checking the mission.log. I mainly was saying it to remind myself to do it. Senility again!