By using a pricing model based up weight both the airlines and the majority of the traveling community would benefit. The airlines they would be gaining revenue based upon the actual weight they are transporting and by knowing the exact weight of the passengers be able to adjust fuel and fright loads accordingly.
For passengers they would longer be subsidizing their heavier counterparts. Take a family with three kids over age 2, currently they have to purchase adult tickets for their kids. They are paying the rate to carry 540 pounds (the FAA states a weight 180 lbs/pax for load planning) yet their kids only weight a total of 180 pounds. On the weight based pricing they would save the cost of 2 adult tickets.
Heavier people actually do use more fuel and when I transport my children it would be nice to get a slight discount for the fact they weigh less. The difference in price will not be much because the weight of things like the seat and toilet and in flight meal will remain the same, but there shouldn't be a ban against it.
It's a business/money decision. And a smart one. Extremely overweight people "spill over" into adjacent seats which then means other people cannot be seated comfortably. So the overweight person should purchase the adjacent seats. Morality and sympathy have nothing to do with the issue. It's very matter of fact. I am an overweight person.
Everyone is different and some people have disabilities so they cant work out of be as fit as others. But to think that they would have to pay more to go on an airplane then the person next to them is a disgrace. There self esteem would be down, being even worse to there health.
But charging on weight alone is not a valid test for finding out how many seats a person would need to use. Width measurement would be a much better way to do it, preventing embarrassment, and ensuring that 200lbs of muscle vs. Fat would not make someone pay more. That way, if the person would encroach over another seat, they would pay for two seats, or maybe upgrade to avoid causing discomfort for others. As far as weight limits go, I think that the width check would be sufficient to monitor if the weight threshold is being approached. Even a body builder would eventually take up more than their share of a row of seats width-wise once they reach a certain weight. The width check would be given for the widest part of that persons body.
It is unfair for airplane companies to charge their customers according to their weight. Men would consistently pay more than women. Pregnant women would pay more than women who are not pregnant. Larger people who spill over into the neighboring seat should do the considerate thing and buy both seats by choice.
I weigh 210 lbs of solid muscle but my girlfriend weights 105 lbs. I weigh double her weight so I pay $400 for an airplane seat while she pays $200? I don't take up two seats. Charging customers according to their weight is unconstitutional. Charging obese people, though, is another story.