Only per mile. Per journey it's the most dangerous transport typically used. Per hour it's about average.
This doesn't matter if you have to make a specific trip (the number of miles is fixed), but that's not always the case. Whatever you do, don't walk, that seems to be the most dangerous common mode of transportation (unless motorcycles are common).
"Aviation industry insurers base their calculations on the deaths per journey statistic while the aviation industry itself generally uses the deaths per kilometre statistic in press releases."
Your point that accidents per journey might be more interesting than accidents per passenger-kilometer is a very good one, however it seems like the data in the table in the Wikipedia article you linked is a bit old ("The following table displays these statistics for the United Kingdom 1990–2000").
If you take a look at the "Fatalities per trillion revenue passenger kilometres" plot in the same article, it looks like flying got a lot safer since 2000 (maybe ~10x?).
The conclusion that flying isn't a lot safer than other common modes of transport when you compare by journey is still correct though... (But maybe it is a little bit safer, or similarly safe).
The other thing is that the statistics for car travel include all journeys by car. You can do a lot to improve your own safety by avoiding the common risk factors: not driving drunk, driving in daytime (that also avoids drunk drivers), not being in an all-teenage vehicle, driving well-rested & so on. If you do that, per journey you'll be safer than in your regular commercial aviation airplane.
> don't walk, that seems to be the most dangerous common mode of transportation
Not walking is also a bad idea, though. I don't have numbers at hand, but I can imagine that a sedentary lifestyle gives you way more micromorts than the risk of traffic accidents when walking to work.
This doesn't matter if you have to make a specific trip (the number of miles is fixed), but that's not always the case. Whatever you do, don't walk, that seems to be the most dangerous common mode of transportation (unless motorcycles are common).
"Aviation industry insurers base their calculations on the deaths per journey statistic while the aviation industry itself generally uses the deaths per kilometre statistic in press releases."
Source: Transport comparisons in https://en.m.wikipedia.org/wiki/Aviation_safety