This article is from the Classical Guitar FAQ, by Joshua Weage (jpweage@mtu.edu) with numerous contributions by others.
Basically, get a hard case. A soft case will not adequately protect
your guitar. Hard cases cost as much as a cheap guitar, but when the
guitar is worth hundreds or maybe even thousands, its well worth it.
Insurance may get you your money back, but some musical instruments
are priceless.
On airways, and perhaps in general, guitars are safe in the hold inside
their hardcases if they have 'fragile' stickers clearly placed on them.
According to many posts lately, most guitars can be carried on and put
in the overhead compartments.
If your going to a hot and humid place then it is a good idea to put a
home-made dehumidifier in the case along with your guitar. This is made
by getting a sponge and placing it in a plastic bag which has holes
cut into it. Apparently, it works in Sunny South Africa :-)
 
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