I'd like to see a system where you get a fixed weight, say 100Kg (the exact number isn't important). You and your baggage get on a weighing platform together. If you're over, then you pay more. This is fair because that's what affects the plane's fuel consumption.

Some friends of mine were stung when they had 25Kg of baggage allowance going out, but the airline changed their policy mid-trip and they were only allowed 20Kg coming back. So they got on the plane wearing their dive gear...

The problem becomes a paradox when you consider birds.

Bird bones are much smaller and less dense than ours. Then you must consider that a bird can already fly, which means that the airplane is not a necessity for them.

In my humble opinion, in light of the prior facts, I do not subscribe to the belief that bone attributes are a reliable means of determining airplane fare.

Or rather, I propose the use of volume, instead.