I bring my markers in my carry-on. Kacey Miyagami showed me how she uses a camera bag to carry them in. There shouldn't be a problem with pressure changes since the markers don't carry the ink in a sealed 'well' but rather in a sort of spongy absorbant material where the pressure will be equal within and without at all times. I keep my markers behind the table while I draw and take them back to my room at the end of each day.