Hi Jena,
Go to
www.tsa.gov. Click on "Traveler's & Consumers" on the top bar (I couldn't get the specific page link because they use frames! Sorry!)....then click on "Prohibited & Permitted Items" on the bar on the left hand side. It is a pretty up-to-date list. All the knitting lists I am on advise checking it as you plan to travel in case there are changes....additionally, it is best to contact the carrier/airport directly, because apparently it is up to their discretion regardless of what is posted. I have heard that plastic circulars seem to pass the litmus test most often.
Further, the knitting lists advise taking along a self-addressed padded envelope in case you are told you can't take X on board...then rather than getting them confiscated, you can just mail it to yourself!
Best wishes & BOn Voyage!