The debate about extra-large passengers - should they have to buy a second seat instead of spilling over into their skinny neighbours' space - is off again.
This time it has been ignited by a decision by Air France and its Dutch subsidiary, KLM, that "passengers with a high body mass" - if you're flying economy class that means anyone with a waistline of more than 135cm - must book a second seat at 75 per cent of the original fare (though if it turns out there are spare seats in the cabin the airline will refund the extra fare).
It's an approach first adopted by the United States airline Southwest which for the past 30 years has required "persons of size" - i.e. passengers who can't sit in a single seat with both armrests down - to buy a second ticket (again, if there turn out to be spare seats in the cabin the fare is refunded).
US rival United puts a slightly different twist on the rule by requiring that passengers in a fully booked economy cabin who cannot buckle the seat belt using a single extender must buy an upgrade.
Other airlines are slowly following suit. Air New Zealand, for instance, says it expects passengers who know they require extra room to buy another seat.
There are good reasons why the issue is becoming more acute: the statistics show we're all getting bigger; fuel consumption is acquiring growing significance for airlines for financial and environmental reasons; and airlines are getting increasingly successful at filling their planes so there are fewer spare seats for large passengers to spill into.
Despite that, in my experience, airlines in this part of the world at least are still reluctant to really grapple with the problem. For instance, Air NZ may "expect" large passengers to buy an extra seat but doesn't seem to take a firm stance if they don't.
Doubtless that's partly for fear of a human rights case and partly a reluctance to offend potential customers... but the end result is that standard-sized passengers still suffer if they get someone oversized in the next seat and still contribute more than their fair share to the fuel bill.
In any event passenger size is only part of the weight issue. Airlines also seem reluctant to enforce the rules on cabin baggage with the result that some passengers continue to fill far more than their share of the overhead lockers and add a disproportionate amount to the payload.
Probably the only truly fair way to deal with that side of things is for passengers to be weighed together with all their luggage and charged extra if they exceed the limit. As a skinny traveller who packs light I'd be all in favour of that.