IIRC it really depends on the cargo. A very cool example I came across was iPhones being fairly heavy relative to their volume while roses were very light relative to their volume. The solution of the air freight company was to fill their aircraft 50/50 with roses and iPhones so that they were both at their weight limit and at their volume limit.

Ingenious on the part of freight company, but roses being transported halfway around the world is an indicator of what's wrong with modern commerce

iPhones being transported halfway around the world isn't? In both cases the difference in labor cost is large enough to make the flight profitable.

It makes sense for there to be only one iphone production line, in the same place as all the factories that make iphone components - shipping the components around and having multiple copies of the production line would probably be more wasteful. That's not really a concern that applies to roses.

Yes, since roses can be grown almost anywhere, and they are 100s of replacement for a rose.

In theory bananas can be grown anywhere, but I believe biology has other things to say.

Bananas aren't flown though. They can be grown in many places, it's just the current supply chain for them is most cost-effective.

Some bananas certainly are flown, although I don't know the proportion of the total.

They were loaded into a flight I was on from Costa Rica to Paris.

it's not a limiting factor but fwiw, air freight market is driven by the value of the cargo. Expensive stuff sitting in a container on a ship is like paying interest on the money invested; the sooner you get it to market, sooner the green comes rolling in.

Weight is more often than not, as far as I'm aware. This also ties into questions about refuelling: there's certainly cases where freighters have a choice of carrying more freight and requiring a refuelling stop _or_ flying non-stop. How much the time-sensitive cargo is paying decides questions like that.

Weight, largely.