"If the [Boeing 737-400] plane is 75% full, one passenger is carried 22.2 km for each liter of fuel burned (52.2 miles for each US gallon of fuel burned). This fuel efficiency exceeds that of almost all cars, when the driver is travelling alone."
The relevant figure, at least as far as the atmosphere is concerned, is L, not L/km. (L/km is a good proxy when comparing two things that travel roughly the same distance)
In Switzerland, despite driving a 4x4 (suitable for hauling goats up the mountain) instead of small convertibles, we burn much less fuel now than we had been burning in California -- mostly due to the fact that we can go several days at a time without using the car.
For instance, I'd calculated a train+bus trip to a remote village on the other side of the country (well, as "remote" and "other side" as CH gets -- roughly 300+ km one way) as having taken about half a liter.
-Dave
