I have used the following on many flights without issue:
Small seam ripper
Scissors from a sewing kit (like these http://tinyurl.com/yjpcrx)
I have loved flying since I learned to knit. Unfortunately, the last flight I went on, I had to crochet. I picked out this blanket I wanted from a 1976 Woman’s Day Granny Squares book, it is so cool. I figured crochet would be as satisfying as knitting. Wrong (for me, anyway). It is 169 granny squares, so I didn’t take knitting to force myself to crochet. There were three other women on the flight knitting, I was so jealous. I wanted to tell them that I am a knitter, not a crocheter… Just 25 squares to go, then I have to figure out how to get the thing together. I bought the yarn for a second blanket, but I’m not sure I’ll have the heart to actually make it. I don’t like things that interfere with my knitting!