This is off topic. But I've been skeptical of the commercial aviation accident risk compared to cars. I'm not saying cars are safer. But using accident count per mileage seems a bit odd, especially when the most risky parts of flying are taking off and landing. A plane travelling 400 more miles doesn't incur much more risk. But a car travelling 400 more miles incur a much bigger risk (e.g. fatigue, car malfunctioning…
I'd say it's accidents per person/hour. And I've read somewhere that the figures used to be similar for cars and airplanes (though aircraft safety is constantly improving, cars probably less).
https://www.bts.gov/content/fatality-rates-mode
For the sake of argument, assume cars travel an average of only 10 mph, and air carriers carry just 50 passengers (low estimates tilt the comparison in favor of cars). That would mean cars had 1.1 fatality for every 10 million hours in 2015. The corresponding figure has been between 0.0 and 0.6 for the last decade, and airlines come out way ahead even after amortizing the 5.8 from 2001 over the following years. And this is with very conservative assumptions.
On the other hand if you add in non-occupant deaths, the numbers might work out better for cars, even after using less conservative assumptions, once you amortize the non-occupant deaths from 9/11.