YP,
I have had different experiences, all somewhat varied, and I am facing the same thing next week when my wife and I are flying down to Florida, then taking a cruse. I am taking my Nylon Stringed Yamaha with me to "serenade" her as we cruse the Mediterannean!
First of all, if it is possible to choose, take a guitar that if it gets lost anyway shape or form, then either you can do without it, or replace it no problem.
The only guitar that fits that for me is my Yamaha. Can get a replacement at any GC store.
Don't lock your case. A big no-no. All the security agents have to do when they see a locked case, is imagine there is something that someone doesn't want them to see. So they break the lock to get in. It happened to me on an flight from Kennedy to London. Nothing was stolen, but it was the hassle of replacing the lock, and fixing the case. And that was BEFORE 9/11. They are much tighter now.
On our flight, I will walk with my guitar to the door of the plane, not the gate, and if it can't fit in the overhead, or in a closet (it is in a SKB type hardshell case), then they will take it to check in, and then at the end of the flight, I will wait at the door way of the plane, and retrieve my guitar.
And this will be my only carry-on. They limit you these days, to one per person.
Traveling with a Strat: my son took one with him to Russia. We undid the neck, by removing the four screws that held it in place, and placed the neck in one suitcase, the body in another. Then, when he got to his destination, put the thing back to gether, and did the reverse when he came home.
The funny thing was, as I was waiting for him at the gate here in the States, I saw this country bumpkin carrying a Fender Strat over his shoulder, no case, strap, anything, just like that, placed it on the X-Ray machine treadmill, picked it up on the other side, and proceeded to walk down to the gate with his guitar. No suitcase, no carry-on, just the Strat. Couldn't be simpler.