Earlier quoted context omitted.
It isn't experimental or unique even if it's rare. It has been done before. I'm not sure why this instance alone got such attention. Regarding the cargo hold problem, the aircraft wasn't carrying just the engine core. The 'pod' is most likely the engine nacelle itself. I wonder if the entire thing would fit through the cargo door (mere speculation). While it's true that the 747 was originally meant as a cargo carrier…
> While it's true that the 747 was originally meant as a cargo carrier I was surprised by this so I consulted Wikipedia. Apparently when the 747 was designed they were convinced enough that passengers in the future would not want to travel subsonically, so they designed the 747 to convert to a freighter, to not have to throw the design away when it's hard to attract passengers due to the "low" 0.8 mach speeds!
For a myriad of reasons ( Boeing failing to make their own supersonic airliner which helped the US Congress banning supersonic flights over the US being one of them), we never got there though, and it seems we never will since the currently planned crop of supersonic airliners ( Boom and co) are specifically targeting the business niche.