Originally Posted by Gwyn
The only ones I know of are more like a circle with little V shapes cut in it. Inside the V and the very bottom is a sharp place so that all you can cut is thread. My suggestion would be to leave your real scissors in your checked luggage and take a little bit of quilt as you go or embroidery on the plane. I've been told crochet and knitting are not allowed either.
MaryMaxim and Herrshners both sell the little cutter.
The last time I flew, I brought my bamboo knitting needles and had no problem getting through security. I was able to knit on the loooooong flight which helped the time pass quickly!