I apologize if this subject has been covered already. I did a search but couldn't find anything.
As someone who travels a lot, and usually brings at least one keyboard along with me I've had a few issues with my keyboards and airport security.
I've traveled with multiple keyboards in Asia, though mostly just my Model F AT, and never had a problem or the slightest issue either as a carry-on, or in checked luggage. Inside a carry-on, they go right through, without even needing to remove them from the bag, no questions asked. The only problems or issues I've had are in the USA.
I've had the following experiences with the TSA at USA airports.
Realforce 86U, no problem going through the scanner inside my bag.
IBM Model M Spacesaver going through scanner needs to be removed from the bag and rescanned by itself.
IBM Model F going through scanner needs to be removed from the bag and rescanned by itself.
IBM Model F's and M's in checked baggage get opened up and examined but processed fairly quickly.
IBM Beam Spring boards in checked baggage get opened up and TSA evidently wants to check these out very carefully. Even checking in 3 hours before my flight, they didn't make it and had to be delivered the next day. Which actually turned out to be a blessing, being I didn't need to haul two 70 pound boxes from the airport to my home.
I've not yet tried to bring any Beam Spring boards onboard, but think I could easily have a problem with the TSA assuming they could be used as a deadly weapon, and perhaps rightfully so.
As far as customs go, I've yet to have any issues there. Been asked a few times by customs, "what's in the box", and I say "computer keyboards". When they look over the huge box and ask how many, I say something like "about 20, but they're all at least 25 years old" at which point they just wave me through.
Ok, I realize that airport security screening isn't an exact science, and your experiences may vary depending on who's doing the screening. Just thought I'd share my multiple experiences in traveling with keyboards in case anyone else has been wondering.