[dTal]

Oh, and fun fact: an Apollo moon mission racked up nearly 3 million passenger miles per flight and did not suffer a single fatality. Even if the astronauts on Apollo 13 had not survived, and the whole program cancelled right then and there, by fatalities-per-passenger-mile a Saturn V to the moon would still be far "safer" than driving, which averages one death every quarter of a million miles.

I think this demonstrates two important flaws with the "passenger miles" concept: 1, miles are not always fungible between modes of transport. 2, intuitively we care more about the risk per trip, rather than the risk per mile.