Comment by rz2k
This reminds of discussions following the Fukushima disaster where one commenter claimed that it wasn't a design flaw, because it was an extraordinary circumstance. I found this appalling, because I do not at all think that was the risk profile that was sold to the public; I think people believed that it was supposed to be designed to safely survive 1000-year earthquakes and the tsunamis that they create.
Likewise, I think that the flying public is lead to believe fuel exhaustion is so rare that when airlines are compliant with regulations, no such disasters across all flights across all carriers will occur during your lifetime.
It's also a communication problem, because labels like "100-year/1000-year event" are easily misunderstood.
* they're derived from an estimated probability of the event (independently) happening each year. It doesn't mean that it won't happen for n years. The probability is the same every year.
* the probabilities are estimates, trying to predict extreme outliers. Usually from less than 100s of years of data, using sparse records that may have never recorded a single outlier.
* years = 1/annual_probability ends up giving large time spans for small probabilities. It means that uncertainty between 0.00001% and 0.00002% looks "off by 500 years".
https://practical.engineering/blog/2025/9/16/an-engineers-pe...