A Flygirl
I always enjoy a debate.

I absolutely agree with the proposition that airlines are out to make as much money as they can and I even think that's a good thing. I did not mean to suggest that they should give discounts to families out of a charitable instinct but rather that that might be a way to make even more money.
You bring up the issue of whether large people are charged more for the seat a six year old might occupy or whether old people face different prices. Old people do face different prices, for airfares as well as all other kinds of things. They generally face lower prices because companies believe old people are not willing to pay as much as younger people and because it is relatively easy to charge different prices for old versus young people. And six year olds are charged different prices from adults. So differential pricing already exists (b/c airlines find it profitable). I was raising the issue of whether an even more elaborate scheme is possible. (Don't know about the relative willingness to pay of fat v. thin people but enforcement of a pricing scheme based on weight might be difficult or socially awkward.)
My suggestion is based on the following notion. Airlines charge lower prices to kids b/c the value parents generally place on flying their kids is lower than the typical adult value for a flight. I would suggest that the value declines per kid. That is, parents with 4 kids are not on average willing to pay 4 times the amount to fly their kids as a parent with one kid. Thus, it might be in the airlines' interest to offer a lower per-kid price to larger families. As for whether they can predict load factors and all that with such a pricing scheme, I'm not sure although I tend to think they're awfully sophisticated at those things.
[This message has been edited by MagMile (edited 08-28-2000).]