SKB 3i-4217-18

I've used this for my guitars for long-haul flights out and back from the UK. It's a proper transport case that lets the guitar retain humidity and protects against any sort of knocks the baggage handlers throw at it. A standard hard case is not enough if you fly and check the guitar into baggage, so use one of these if you want your instrument to emerge at your destination exactly as it left. Good points: massively solid construction and protection for your guitar. Bad(ish) points: rather heavy, has to be checked in as 'oversized luggage', and Customs people think it contains guns (it is, after all, a military-style case). I like it a lot.