Comment by kube-system

This is really helpful and I think I understand now.

The approach is basically “accounting for everything that might go wrong to the best of our experience, including problems arising from the complex interactions between the airplane and supporting ground systems and processes, this is how much fuel you need in the worst case scenario. And now lets add more to give us a cushion, and we will treat consumption of this last reserve as tantamount to a crash.”

This is exactly how it is in this case. Any consumption of the fuel reserve would result in an investigation, this is a very extreme case and it may even result in a change in the rules depending on the root cause.

Yes, exactly. The day it's normal to eat into the allowance is the day we start seeing planes falling out of sky for lack of fuel again. The only way to prevent that is to treat 30 min of fuel as seriously as you would 0 minutes.

Yes. Similarly, safety needs to be there even after the aging of materials over product lifetime. So basically when aging is the only variable to be considered end of life date is the worst case scenario.