I carried a McIntosh MC-225 tube amp on a flight one time from Atlanta to Philadelphia in 2008 or so. It was in a "custom" cardboard box with a lot of duct tape all over it. Very shady looking, but I had to go with what I had on hand at the time. My friend thought I was going to get a full body cavity search, but I decided to risk it anyway because I was already checking a C-20 preamp and didn't want to check this as I had no way to safely pack it for that. You want to know what happened? Absolutely nothing. They didn't even ask me what the hell it was and they sure didn't ask me to open it.
Another time, also from ATL to PHL, I carried on an Eminent Technology ET-2 tonearm. This time they made me open the box. They were not happy at all. Upon sending it through the X-ray machine:
"What's is it?" they said.
"A tonearm for a turntable," I said.
"Remove the instrument," demanded security (they were not happy!).
I slowly opened the box to reveal the arm. I don't think I even took it out. I guess they realized how delicate it was by the way I opened the box and decided that it could never be used as a weapon, I don't know. He certainly did not think, "Oh, yep, that's an ET-2 alright."
"Proceed," they said.
I was sweating bullets!
A turntable with a conventional arm is a little more recognizable, so I think you will be OK as you're sure it will fit in the overhead compartment or under your seat. The dimensions of these compartments are easy to find if you do a quick search online.
