I just can’t seem to put my finger on it... That Kinja crop though.
Quantas used one of their 747’s to transport a spare engine from Sydney to Johannesburg. Full story on the Quantas website which is where I got the photo and YouTube video from. On some of their 747’s there is an extra set of anchor points between the port inboard engine and the fuselage that they can use to transport an extra engine. The engine is simply dead weight, so they have to account for the extra drag on that side and the plane burns extra fuel. Obviously the extra fuel burn is cheaper than chartering a cargo aircraft to transport the engine. The engine that gets removed will then get shipped back to Sydney via cargo ship.
Here is a screenshot of the extra engine mounted under the wing. It looks to me like it is missing the fan. Maybe F86sabre can comment on this, but I wonder if they reuse the fan from the other engine, or is there a new fan that is being transported in the cargo hold of this aircraft?