Years ago, I bought a used M 4 + a 35mm f2 Summicron. I mostly used it around the acreage we lived in then. It worked well, except because I am left eye dominant, I was frustrated because I felt I never realised the full benefits of the viewfinder. 🙁
But, to return to the question, I took a short commercial flight, and put the M4 in the bag I used every day in those days. (Sorry, I can't remember which bag it was, but I do know I'd never had any problems with it). I put the bag in the overhead compartment. There was nothing unusual about that compartment. When I arrived, I opened the bag and discovered the film advance lever had come off the body. I put it back on the spindle (?), and everything seemed Ok, except I never trusted the camera again - certainly I never felt I could absolutely rely on it; not like every Nikon I ever owned. They never let me down!