According to the Huffington Post, the U.S. Transportation Security Administration allows airline passengers to take crochet hooks as carry-on items. Most knitting needles are permitted on board, as well.
However, the Huffington Post warns that certain TSA agents are more cautious and may not approve craft items. Some handwork tools, such as circular wooden or plastic needles, seem to be universally acceptable. At security checkpoints, it is recommended that crocheting and knitting travellers put their tools directly into the plastic bins to simplify the inspection process. Although the TSA lets knitting needles through security checkpoints, the TSA indicates that circular thread cutters or cutters with internal blades are not acceptable. These cutters must be transported in checked luggage.