A few years ago, I bought a guitar in Japan and comes with a hard case. They had it checked-in and when I reached Changi, it was among with other luggage on the conveyor belt. No damages so far. This trip is by way of SIA.
And again, just recently, I bought a guitar from Japan and brought it here in Singapore last week. I had them hand carried but inside the plane, the stewardess asked me to put it in an "extra" overhead compartment (the one on top of the changing table for babies) but the guitar was not able to fit. So we put it in a compartment used by the plane's crew thus my guitar was standing on top of a luggage and it's position is being stabilized by the guitars neck leaning towards a clothes bar and we did not have a smooth landing. sheeesh...
Anyway, once I got home, I inspected for any damage but so far found none. This is my experience for JAL and by the way, my guitar was in a thin padded case.