There seems to be no absolute solution to the question of knitting needles on airplanes; it seems to depend on the airline and the situation. But scissors or knives are a definite no.
A recent impromptu, last-minute brain storming in a parking lot with a lady who was off within hours to England to greet a brand new, first, grandchild and who had finished all the pieces of her knitting but needed to put them together and had a plastic, blunt end needle for the actual sewing but needed someway of cutting the yarn ………. She had heard of a nifty little cutter sort of hidden in a circle: local stores were all out of it. She took out her keychain and looked hopefully at the tiny knife attached to it but we both shook our heads.
We stared thoughtfully at each other. "Your teeth, I suppose," I suggested and we both frowned. Then, of a sudden – likely the mention of teeth – dental floss popped to mind. "Dental floss!" I said. I think I may have shouted. She looked puzzled for a teeny second and then she got it. "Dental floss!" she said. "With that neat little cutter."
When I got home I had to try it. It works!
Necessity and grandmothers and inventiveness and all that.