> one of the safest modes of transportation

How far do standards have to fall before that's no longer true?

Recall also that aviation is the safest in aggregate, but the severity of each individual incident tends to be much worse than others.

Hard to find up to date data, but looks like about two orders of magnitude, from ~5 deaths per billion miles to 0.05.

(Miles traveled is somewhat charitable to airlines and assumes trips are fungible between planes and cars.)

I'm not sure how you mean it's "charitable?" Could you explain?

Sure, sorry. Planes cover distance very quickly, and people use them for e.g. a six hour flight covering 4000 miles that they would not otherwise drive; this situation makes planes appear safer "per mile" than alternative valid metrics like "accidents per hour of travel" would.

What does the severity of the average incident have to do with whether I use a particular mode of transit?

We could add lots of fender-benders between taxiing planes to push down the average severity of each plane "crash." Then they would still be less deadly per mile travelled, but also less severe per incident on average than other modes of transit.

I wonder how unreliable a specific model of commercial aircraft would need to be in order for it to no longer be the safest mode of transportation.

According to [1], commercial planes are about 3 times safer than buses per passenger mile (edit: passenger hours, sorry). That doesn't sound like a large enough margin to prevent certain more accident-prone models from earning the "deadlier than a bus" badge of shame, especially since the average is skewed by extremely reliable widebody models like the 777, A340 and A380. Meanwhile, commuter planes already suffer from a higher fatality rate than pickup trucks, while private planes are second only to motorcycles.

[1] https://turbli.com/blog/the-safest-transport-modes-ranked-by...

> According to [1], commercial planes are about 3 times safer than buses per passenger mile.

Uh... the "Fatalities by passenger miles" chart in that article says that fatalities per billion passenger miles are 70 times lower for commercial planes vs. buses.

And in fact if you normalize to actually comparable transportation modes, my guess is it's even worse. The overwhelming majority of bus miles are driven on urban transit routes at low speed. You'd want to split out long haul (Greyhound et. al.) buses to compare to aviation, and highway travel is always going to involve more fatalities.

Basically, even knowing that it's probably the most dangerous jetliner in decades, I'd still view a 737 MAX as an extremely safe travel option.

Someone pointed out that if you normalize from "fatalities per passenger mile" to "fatalities per trip" the airplanes don't look quite as good.

Fortunately, one normally doesn’t take a 737 to the corner store, drop the kids at school, or go out for lunch. The only thing normalizing by trip tells us is people take lots of car trips.

Well, yeah, because airliners are extremely large. If you do the same thing for cruise ships, they surely look horrifically dangerous! "Heart attack fatalities per trip" are off the charts.

When a regular person asks "is this safe?" they mean "is it safe for me?", not whether someone else on the vehicle might get injured.

Surely no one is discussing dying of other causes here

Uh... it was an example showing the flaw in the logic. You can't compare a 300-seat jetliner to a motorcycle in a metric of "fatalities per trip", because that doesn't give you any useful information about the subject under discussion ("am I going to die on this trip?"). It's just bad risk analysis.

Luckily no one was doing that. By your logic we shouldn’t compare anything because far more people travel by car than plane in a given year.