[ItalianPizza64]

I had the opposite feeling: how had nobody yet thought of utilizing sails to improve fuel efficiency for these huge cargo ships?

I don't know much of ships and their fuel consumption, but I would guess that any percentage point of fuel saving would quickly add up to a significant cost reduction

[detaro]

The idea and proposals have been around for decades.

[tawm]

Usually the ship's owners are not the ones paying for the fuel, that's on the charterer's account.