So I (and several others) had a debate on Twitter today with Megan McArdle about children on airplanes. Megan’s basic argument, as expressed in this tweet and elsewhere is that, out of courtesy for others, parents of small children should avoid bringing them onto airplanes except when absolutely necessary. Here’s why Megan is wrong:

1. The vast majority of small children on airplanes make no noise at all, or make easily ignored noise, or cry at takeoff and landing because their ears hurt. None of those is a big deal for anyone. It’s only the worst-case scenario, the child crying throughout the duration of a long flight, when the inconveniencing of others becomes a significant consideration. But among all the small children who fly, what percentage cry through a whole flight, or even much of it? My guess, based on thirty years of flying, is maybe one-tenth of one percent. Do we really want to recommend a policy for everyone based on what happens a tiny fraction of the time? Hard cases make bad law, and bad ethics too. It’s what you might call TSA logic.

2. Megan says that when a child cries through a whole flight, “The bulk of the cost of a screaming baby is born by the fifty-to-three-hundred other passengers, not parents.” First of all, even a screaming child won’t be heard throughout the plane, and will be a significant annoyance for, say, fifty people on a full flight. That’s a lot of people, you might say, but let’s be careful about how we calculate these things: we don’t want to say that fifty people suffering some frustration is fifty times worse than one person suffering it, or else we’ll have to end up agreeing that the net amount of pain American commuters go through on the highways each day equals the pain experienced in the Armenian genocide. Fifty people (or for that matter 300) being annoyed during their flight doesn’t amount to all that much suffering. And the number of people affected will be diminished if some of the passagers have headphones or earplugs. (By the way: why don’t more people bring earplugs on flights? The same reason that people don’t think to bring crash helmets when they drive: the kind of problem that Megan wants to avoid happens so rarely that they don’t think to.)

3. But let’s say that I know that my child is going to cry through a whole long flight. (No one in fact knows that, and again, the chances of that happening are very small indeed, but I’ll grant the next-to-impossible for the moment.) Should I refrain from flying in order to avoid inconveniencing my fellow travelers? I suppose that would depend on why I am traveling. Let’s consider a common scenario: We’re going to Disney World. To avoid subjecting people to a crying child on a flight to Orlando, we could stay home; or we could choose a different vacation destination; or we could drive to Orlando. All of those choices impose a pretty significant cost on my family — even driving, which Megan seems to recommend. If the problem she wants to avoid is children crying on a long flight, then almost by definition Orlando is going to be beyond reasonable driving distance. If it takes us two days to drive to Orlando and two days to drive back, we’re losing a good chunk of our vacation. Should we do that in order to avoid making people on the plane listen to our screaming child? Would that be “common courtesy”? That’s setting an extremely high bar for the “common.” (It would be interesting to poll the people affected — our fellow passengers — on this point. Would most fliers think that parents who know their child is going to cry for an entire flight have a moral obligation to refrain from flying? to stay home? to go somewhere for vacation they don’t really want to go? to leave the children with … someone and take a vacation on their own?)

The one time I can remember having to listen to a child cry on an airplane for hours and hours came on a transatlantic flight. It was pretty miserable; it went on and on and on. But again it was a transatlantic flight, which means that (a) there were no other reasonable transportation options — should the family have taken the Queen Mary? — and (b) they weren’t likely to be traveling on a lark. And though I sat quite close to the family I didn’t suffer nearly as much as the poor parents did, who tried everything possible to quiet their child and were evidently shattered by the time we touched down. So yes, it was miserable, but it was a freak situation, and just tough luck for everyone concerned. These things happen. You don’t tell millions of people they shouldn’t fly because there’s some tiny chance, not of catastrophe, but of mere annoyance. That’s just absurd.

Also, I can’t believe I’ve written so many words about this.