I was once in the back of a 747, on the left side, when I noticed that the inboard flap section was jiggling about, even though it was retracted. I tried to remember if that was normal, and was about to get up and look at the other side, when the captain announced that any turbulence we might notice was on account of the extra engine under the wing, being ferried as a replacement for a failed one.

A question, for anyone who knows about these things: when an engine is being ferried like this, are the fan and compressors locked in place, or allowed to spin in the airflow? I would have thought that locking them would impose unnecessary loads on those parts and create extra drag and turbulence, while allowing them to rotate would require lubrication?