What to crochet on long flight?

So at the end of July I will be going to Switzerland. It is about a 9 hour flight each way and I was wondering if anybody had any ideas as to what I could crochet on those flights. I will also be spending a long time going between cities and I cannot bring much extra stuff, so that means not much yarn, one, maybe two skeins. Do you have any projects I could do with not too much yarn that might take a little while?