My violin got a nasty split in the top on a trip to the States. I thought it was cold/dryness/string tension. But the guy I took it to said that it was almost certainly impact damage.

My hard case is a thermoplastic one - looks a bit like a Star Trek photon torpedo. ;-) I thought it was pretty tough, but looking back, I suspect that it simply buckled far enough under an impact or crushing enough to bash the bridge, but then it sprang back so that there wasn't any external evidence. So if you're flying, better going with a hard case made of plywood or some other non-flexing stuff.

Graham.