When I travel, I always put my yarn in a Walker Yarn Case. It keeps my skein of yarn neat and tidy in my seat. If my yarn should fall on the floor of a plane or train, the case keeps it from getting dirty and unraveling. Have you all seen the charming video of the ball of yarn that rolls down the aisle, and the passengers roll it back up for the knitter? Well, that will not be me with my handy dandy yarn case.
The last time I flew, I was working on a project that required my notions tin to be on hand. I needed my tape measure and stitch markers along the way. So I popped my notions tin into my yarn case, and, voilà, all of my knitting supplies were all buttoned up in one little package. Even if it is a tight fit, that is ok as long as you are pulling from the center of the skein.
If you want to see what I keep in my notions tin, read my blog post on my notions tin.