Official guidelines

From the Transportation Security Administration website:

Transporting Knitting Needles & Needlepoint

Knitting needles are permitted in your carry-on baggage or checked baggage. However, there is a possibility that the needles can be perceived as a possible weapon by the TSA screener. TSA Screeners have the authority to determine if an item could be used as a weapon and may not allow said item to pass through security. TSA recommends the following when bring knitting needles on an airplane:

• Circular knitting needles are recommended to be less than 31 inches in total length
• We recommend that the needles be made of bamboo or plastic (Not Metal)
• Scissors must have blunt points
• In case the screener does not allow your knitting tools through security it is recommended that you carry a self addressed envelope so that you can mail your tools back to yourself as opposed to surrendering them at the security check point.
• As a precautionary measure it is recommended that you carry a crochet hook with yarn to save the work you have already done in case your knitting tools are surrendered at the checkpoint.

Most of the items needed to pursue a Needlepoint project are permitted in your carry-on baggage or checked baggage with the exception of circular thread cutters or any cutter with a blade contained inside. These items cannot be taken through a Security Checkpoint. They must go in your checked baggage.

Just in case you were wondering.