Quite frankly, I'd rather travel business class. Let the obese and/or the Sweaty Bettys' go cattle class. OR, at least have it where there is adequate space for everyone.
I know that there are medical reasons. If you are having steroids whilst having chemo for example, the person generally will balloon in weight because they are always hungry 7 hours a day 24 days a week. Something I never had thankfully.
However, it starts to become a grey area, as some people are just heavy by nature.
If, IF, however, it's just because they like too much cake and it's their own fault, then, yes, charge them extra!
Ironically for being on a forum like this, I don't really have this problem as I only fly when I really have to. I like to watch the countryside passing by instead of boring cloud and distant land below see, even if it takes me several times longer to do. Not because I have a thing about flying or anything, don't get me wrong, I LOVE heights and flying!
Last time I flew was in Nov '06, and even then it was simply because I had to be in 2 places at one as it were


I use flight as a tool when I am in a hurry/ don't have a choice.
Even the first first time I flew for more than about 10 mins was when I was 17 (BA from Glasgow to Zurich via Heathrow), and I loved every minuite of it (getting to ride extensively in the cockpit helped of course!).
The other irony of this is that, I have a problem with my thyroid, meaning I cannot gain any weight. I have been the same weight since I was about 15, so I'm not likely to flounce over into someone else's seat.
Roarer McToothpick - 9 stone.
'Whooo ate all the pies ....'.