Ultimately while the principle is good - and, as an overweight person, I'd have no problem paying more if it was done fairly - no airline would ever introduce this fairly. Once they've raised the price for fatter people, why, as a business, would they lower the price for thinner people to balance it out? Why not just take more profit?

Think back to when smoking was banned on most airlines, the airlines didn't think "great, now we can give our customers an even better service for the same price but without that smell that non-smokers hate", they thought "cool, now we can massively cut down on how much air circulation we do, meaning less in-plane oxygen, and keep more profit for ourselves".

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This debate may sound discriminatory, but in fact what economists term price discrimination - charging consumers who buy essentially the same product a different price - is a common feature in the modern market.

Surely the argument is that you aren't charging consumers differently for the same product, you're charging them differently for different products - the same way you pay more when shipping a heavier package through a courier firm or USPS/Royal Mail.