There have been a number of questions that highlighted the fact that the 747 could ferry an engine on an underwing pod.
Was the 747 only capable of ferrying 747 engines? Or was it possible to ferry engines for other types of aircraft?
If it can only ferry 747 engines, is there, or has there ever been, an aircraft that can, and has, ferried engines of other aircraft types?
Edit: Following the comments and the one answer posted to date - ideally, I'm looking for cases of aircraft that can ferry engines externally for other types of aircraft. However, if no such case exists (and I suspect this to be the case), it would be nice to see more comprehensive details of how engines are ferried around the world (I'm sure i.e. Qantas won't always use sea cargo, nor an An-124 to)