I had pre-paid for oversize luggage with Jetstar on my return trip from Japan, I asked when checking in if my guitar could go in the cabin locker "no" but the website says it can "No". I'm sorry but the website says there is a 2m high locker suitable for musical instruments on this type of plane. "NO!" Obviously doing anything out of the usual is too much for Jetstar staff. The guitar arrived safe and well in its fender hard case but don't expect much from Jetstar staff.