Here is my Airline Safety Scarf. It is named as such, because I knitted it on the plane to and from New Zealand, but also because I think the stitch pattern looks a bit like a mesh safety fence.
It was a bit embarrassing flying over to NZ - I'd managed to pack my "bits & pieces" bag in my carry on. OOPS. There I was groaning inwardly at the woman in front of us who had containers of moisturiser bigger than 100ml, when my bag had to be searched because of 'metal objects'. The security guy went through my bag. A couple of safety pins, a container of pins and two small stitch holders were confiscated. The 1mm crochet hook and cable needle were fine. I'm still trying to figure out what basis they use - pointiness maybe?
The scarf was knitted on two plastic crayons with elastic bands on the ends. It used up a bit less than one ball of Cleckheaton Studio Mohair (a have a few balls sitting in my stash in case of an emergency).
This is the second scarf I've knitted on plastic crayons. The tougher carry on requirements rule out a lot of standard knitting implements. I normally pack my crayons, yarn and a reel of dental floss (to cut the yarn).
If you want to knit your own, cast on an odd number of stitches (I used 15). Knit the first row, the K1, * YO K2tog. Repeat from * to end. Keep repeating the second row until the scarf is as long as you want (or you get sick of knitting with plastic crayons), and cast off. Easy.