I often take my Martin Backpacker. It has many air miles on it and is usually in the overhead compartment. Where things can go wrong is when you need a smaller commuter leg to your flight. They often don't have much overhead storage if at all. In all my travels it only has one tuner slightly bent (still functions perfect). Even if you have a full size guitar, use a soft gig bag or they might require that it goes in with the luggage.
As with all things concerning the air lines, we are at their mercy.

Respect,
Col. Andy & "Wildcat" Pam