Flying: weigh more, pay more?

I saw an article earlier discussing whether people who weigh more should pay more to fly. (It reminds me of one of Tim Harford’s ‘Dear Economist articles’ on how to split a taxi fare on a trip home after a night out when a group of friends are going different distances).

The author states that:

Friends with whom I discuss this proposal often say that many obese people cannot help being overweight – they just have a different metabolism from the rest of us. But the point of a surcharge for extra weight is not to punish a sin, whether it is levied on baggage or on bodies. It is a way of recouping from you the true cost of flying you to your destination, rather than imposing it on your fellow passenger.

But I think he may be in danger of missing the woods for the trees. It’s true that the cost of flying is directly proportional to the weight carried, but almost all of that weight is the plane itself: a passenger on a A380 at maximum takeoff weight is about 0.01% of the total. Differences in passengers would run at an order of magnitude less. If you did want to charge according to weight, then the fixed cost of moving the plane itself (from which all passengers derive the same aerodynamic benefit) should presumably be shared equally amongst everyone, and then the smallest of deltas added on for individual weights.

Indeed, the data point given in the article is that carrying an extra 1kg from London to Sydney and back again on an A380 costs an additional… answer at the bottom, under the fold.

I typically fly a few times per week, and my answer to friends who ask what I think about the environmental consequences of this is that at the margin, I don’t think I make any difference. If I didn’t fly, I would be significantly financially poorer, yet the environment in no measurable way any better off. Tens of billions of humans will be responsible for dangerous climate change should it occur (it’s from accumulated excess CO2 in the atmosphere, so you need to add up the contributions of everyone from 1850ish, up to say 2050ish) and I’m going to be an infinitesimal portion of it. Tragedy of the commons, yes. (And it’s only looking at one side of the equation anyway, think about all the benefits accruing to other people from the consulting project I’m working on…hmmm.)

People sometimes take issue about me considering myself to be the marginal passenger, rather than an average one, which is a reasonable point, not withstanding the point above regarding the relative weight of the passenger to the plane. Of course, at some point the lose of one more passenger could cause the  airline to drop the route, and I could [not] be that passenger. I read an article a few years back that suggested that whilst the scenario can play out like this in the US, in Europe typically Airline A might keep operating unprofitable routes in order to tie up take-off and landing slots so that competitors B,C, and D are unable to use the slots to compete on the route/timing that is super profitable for A.

And anyway, wouldn’t the plane not just be deployed on another route? If you want to reduce the contribution to global warming from air travel then you need to stop planes moving, not passengers flying on them. Therefore reduce slots, rather than tax passengers more. I guess that would raise governments less revenue though, all things equal.

And, if you’ve read this far, the cost of carrying an extra 1kg from London to Sydney and back again on an A380 is:

$1. Really not a lot.

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