I was just thinking about this the other day. It seems that the justification for charging extra to overweight passengers is that their encroachment on others' seats inconveniences and causes discomfort to other passengers.

If so, then why are lap children allowed to fly for free, and younger children allowed to fly for half price? We have all had our flight's enjoyment impaired by screaming children who caterwaul throughout most of the flight. Southwest charges double to "POS" and then refunds if the flight is not full. Perhaps airlines should charge double for children under 4, and one and a half for children between 4 and 10. Then, if they don't scream during the flight, the money can be refunded.

Or otherwise, it might be better to recognize that we all live in a communal environment, and we need to put up with a little discomfort in order to function within society. In which case, neither overweight people nor people with children should be charged extra.