Flying with a guitar?

Get a hard case designed for travel to protect the guitar. You may or may not be able to carry it on the plane depending on the airline, the size of the plane ,and how full your flights are. Read each airline's baggage rules, they all cover musical instruments in detail. I would plan on having to check the guitar and be pleasantly surprised if you don't.

The most reliable information will be from the airline you are flying. For example, here is info from United: https://www.united.com/ual/en/us/fly/travel/baggage/fragile.html

Call the airline? I would be particularly concerned if I was flying a budget airline. I suspect they would charge you extra. I've flown domestically on Alaska, Delta and Virgin with banjos, violins and mandolins as carry-ons. Those airlines let me put the instruments in the first class closet.

Avoid United Airlines. :)

Any chance you might be thinking about acquiring a new “axe” over in Europe? I’m not a guitarist, so I don’t have a personal experience to relate, but I wonder if TSA and other air security personnel have ever seen Quickdraw McGraw cartoons from the 1960’s. When dressed as El Kabong, he’d “kabong” characters over the head with his guitar...using it as a weapon, which would be frowned at nowadays. I remember a 1973 Let’s Go Europe student guidebook with a drawing of a bunch of students hanging around an airport departure gate, including one hippie-type dude strumming a guitar. Nowadays it’s people listening with their headphones plugged into an electronic device, but hopefully a guitar isn’t now unflyable without paying hefty baggage fees.

Well, we'll be flying different airlines for the different legs of our journey but the main one is Norwegian Air out of JFK. I couldn't find anything on their website about guitars, only weight limits for carry-on and checked.

Not looking to buy a guitar; the one I want to bring is one I constructed myself. I have no case or gig bag for it, at this time, but intend to make one or the other to comply with whatever is required. But if it's too much of a hassle I'm prepared to ship it ahead.

mbv49, my understanding is that there is a specific regulation in the US, that requires carriers to accommodate guitars in carryon spaceif available. But that's US rules, not necessarily applying to international travel. But if you do that, and you take up three passengers worth of precious carryon space with your guitar, you will be cursed and hated for it.

(edit) google "flying with guitar" and you'll find a plethora of articles on the rules. Doesn't mean you wont get hassled at the gate.

Yo Yo Ma's cello flies in its own first class seat. Airlines have "Special Baggage" policies. Delta's example:
https://www.delta.com/content/www/en_US/traveling-with-us/baggage/before-your-trip/special-items.html
Under the "Musical Instrument" tab:

Musical instruments and/or equipment are accepted as checked baggage,
carry-on baggage or cabin-seat baggage — depending on its size and
shape — on Delta and Delta Connection® carriers flights¹. Please help
us to keep your instrument safe by bringing it in a hard-shell case.

What Instruments Can I Carry On?

Guitars and other smaller musical instruments, such as violins, will
be accepted as your free carry-on baggage item on Delta and Delta
Connection® carriers flights¹. These items must easily fit in the
overhead bin or other approved storage location in the cabin, based on
available space at the time of boarding. Musical instruments may be
gate claimed at the discretion of the passenger and as a result of
limited overhead space.

What Instruments Might Need Their Own Seat?

You may purchase a full fare ticket for an item that you feel is too
fragile to be handled as checked baggage. You may stow the baggage in
any passenger seat with a bulkhead or divider in front of the
compartment. The following restrictions apply. The item must: etc

You've gotten lots of good advice above. Here's the guidance from the Berklee College website: https://www.berklee.edu/summer/registered-students/travel

Can't speak to your 'real' question- but as a former player, PLEASE either detune (loosen) all strings, or remove them before flying. Changes in humidity and air pressure can play havoc with instruments. A WELL CONTRUCTED hard case with sufficient padding is really the only way to protect your guitar. Ask for help from guitar stores or other (preferably professional) players.

I wouldn't take the risk and take the guitar with you unless you're moving to Europe. Are we speaking of an acoustic or electric guitar? You would need a hardshell case to bring it with you, however, you won't be able how it's handled unless you take it with you onboard. Does it contain rosewood? I heard there might be some problems when going out of the USA with anything that contains rosewood.

Check this article on regulation of a rosewood export

Thanks for all the observations and suggestions. To clarify a couple of points. I built this (electric) guitar myself and am confident that I can build a secure hard case for it. I can't buy a pre-made case; there are none available that it would fit. I'm also aware of the CITES regulations regarding the import/export of anything with rosewood however those regulations are regarding guitars being shipped internationally for sale. This guitar does have a rosewood fretboard but it is not for sale.

I believe I have, basically, two options. The first is to ship the guitar on ahead to my son in the UK. My job is in online sales and we often ship guitars to destinations all over the US. I know how to securely pack a guitar (in a case or not) for shipping. My other option is to remove the bolt-on neck and thus pack the guitar into a smaller package that would more readily be acceptable as carry-on. I've actually done that before without running into any problems (other than removing the neck, reattaching it and then removing it again for the journey home). This time, however, I'm more inclined to ship it to my son. I have dual UK/US citizenship and my wife and I intend to ultimately return to retire in the UK (or maybe Portugal for the climate, cost of living and because a good friend is a member of the national assembly) so if I send it on ahead it'll be one less thing to worry about when it comes time to return home.