Me and my chap flew to Paris last week, we both got our instruments (fiddle and pipes) on as carry-ons with no problems. However I had 2 sets of bellows-blown pipes with me but not quite enough space in my pipe case, so I put one bellows in the rucksack that was going in the hold. On the return flight, we got called through by a serious-looking Gendarme and made to unpack the bag, to much hilarity all round when we worked out it was the bellows that was the problem - it had shown up on the x-ray at a bad angle and they thought there was a handgun in the rucksack!