I think the passenger miles statistic is baloney (calculated by multiplying the number of passengers by the number of miles travelled), and I'm a bit sick of seeing it trumpeted everywhere to claim flying is vastly safer than driving. The collective risk of everyone on board the plane is meaningless to calculating risk to your personal safety. At least for me, the fatality rate per journey, per hour of travel, or at the very least per mile I myself am travelling, is far more relevant. According to one source, flying is actually three times deadlier per journey than driving (fun fact, this is the metric aviation industry insurance companies use), but about four times safer per hour travelled. So flying certainly can be safer than driving in the right context, but these crazy "100x safer than driving" stats are kinda useless and take a lot of "creativity" for airlines to arrive at.

source: https://en.wikipedia.org/wiki/Aviation_safety#Transport_comp..., citing Beck, L. F.; Dellinger, A. M.; O'neil, M. E. (2007). "Motor vehicle crash injury rates by mode of travel, United States: using exposure-based methods to quantify differences"