This is framed misleadingly as a risk calculation, but the math is unfairly generous because planes go a long way and carry a lot of people. It is not a valid calculation for "how likely am I to die if I get on a plane".

Imagine if each plane carried a million people, and traveled a million miles in a single flight, and 1 plane in a dozen vaporized all its passengers. By the logic of the post, you would crunch the same safety number - "passenger miles between accidents" - but we would not call such a mode of transport safe because you have a 1-in-a-dozen chance of death.

If you are going to sum up passenger miles, rather than aircraft miles, you need to compare that against passenger-accidents, rather than aircraft-accidents. Each aircraft crash kills about 100 people at a time, so that "2 light years" figure is two orders of magnitude too generous, right from the start.

There are other arguments to be made about "passenger-miles" as an entire concept (air miles are not always fungible with other modes of transport, and a plane which explodes on takeoff 1% of the time is not safer if you fly it farther each flight) but I'll stop here.