Message on the JAL website:
“At JAL for outgoing instrument service, we offer small and large instrument cases to support our customers on trips with important instruments.
Now in response to customer feedback we have dispatched guitar sized cases (137cm x 44cm x 21cm) to all airports offering domestic flights. Until now, in such a case you would have to check it as fragile baggage, but from now you can ask for our guitar-exclusive case. JAL will continue to provide you with the best possible service in the future.”
Good thinking. More here.