When the EPA rates a vehicle's fuel efficiency, it doesn't look at the number of seats in the car, it just tests out how many miles it can go on a gallon of fuel. This is a fair way to compare cars, but if we allow ourselves a little bit of mental reconfiguring, we can find an interesting way to compare airline travel with long-distance road trips.

The Wall Street Journal took a look at the relative fuel efficiency of different airlines using the "seat miles per gallon" idea. If we compare the fuel efficiency of various planes divided by the number of seats on those planes, it turns out that flying isn't all that bad compared to driving alone in a car. In fact, the big U.S. airlines averaged about 64 seat mpg in 2009, according to Department of Transportation numbers the WSJ crunched. Of course, your mileage will vary, depending on traffic (air congestion is a killer here), driver/pilot style and the number of people on the plane, but it's still a pretty impressive figure.

Of course, a post like this is just asking for caveats, so here we go: for one thing, the airlines are burning high-octane jet fuel, not standard gasoline. And, of course, using the seat mpg standard, you can double the rating for your car just by grabbing a friend for the trip. Still, a lot of the things that save fuel in your car also work in a plane. Also, plugging in helps with efficiency. As the WSJ writes:
Alaska [Airlines] changed procedures for ground workers so that electrical power is plugged into arriving flights within five or 10 seconds of setting the parking brake, letting pilots shut down engines faster. That and other changes on the ground have saved an estimated 1.8 million gallons of gas a year.
Not bad, huh?

[Source: Wall Street Journal | Image: emrank – C.C. License 2.0]