In the post-9/11 scare, airlines became so uptight about security that they banned an array of carry-on items, including knitting needles and crocheting needles. The demographic group most affected by this policy, of course, also comprises the one set of people least likely to employ such needles as a weapon.
Thankfully, sanity now prevails at most airlines, and passengers may bring on board whichever fabric and needles they want. Well, almost: don’t try lugging your vintage singer sewing machine into the cabin.