Originally Posted by
blubak
That is correct as far as the 747 is concerned BUT it was only if the operator had optioned that facility & the placement of it was inboard of the #2 engine.
Qantas had at least one 747 that was optioned that way (
https://simpleflying.com/qantas-747-5-engines/) and if I recall correctly it had the bits to ferry a CFM56 if needed. I have no idea how they'd do that now. Perhaps road freight really is the only option?
(I recall a QF 737 a number of years back landing at Perth in stiff gusty crosswindy rainy awful weather on both the left gear and the left engine then needing to wait for a spare to be ferried across. Apparently the engine strike happened so quickly none of the passengers and crew actually noticed until they got to the gate!).