The environmental cost of flying

Minderbender, a loyal MM reader, asks:

How should we think about the environmental costs of commercial flying?
It seems as though the average cost is high, but the marginal cost is
quite low. When I fly across the country, it doesn’t cause any extra
flights, it just makes the one I’m on slightly heavier. Yes, the
increased revenues might give the airline an incentive to increase the
number of flights, but this effect seems very weak – much lower than
the average cost of my flight (the consumption of fuel divided by the
number of passengers). Maybe I’m just miscalculating?

I think about this every time I fly.  A simple model of route expansion is that higher demand increases the number of total flights by some probability.  For the system as a whole, the decisive flying unit has to come somewhere and there is no reason why, on average, it can’t be you.  In other words, at least in stochastic terms you can’t escape the blame.

A second simple model of route expansion is that gates and other airport facilities are scarce and underpriced relative to demand.  When demand goes up, supply is not very elastic and mostly they raise price rather than increasing output.  Those who feel very guilty should prefer this second model.

The more they cut back on flights, as they have been doing, the more likely the first model is true.  The second model is most likely true if you are flying into regulated foreign markets although I believe the Europeans are now opening up for U.S. carriers.

You might ask comparable questions about eating meat and killing cows.  If you’re worried about your net impact, eat animals from countries with very privileged, monopolized and highly regulated, supply-inelastic livestock sectors.