Needles Have been approved for travel since shortly after 9/11 on American carriers.
However International flying can be sketchy. If you are traveling out of the USA you will probably be ok ,traveling into the USA is always a risk.(different counties different rules.)
I do have some recommendations. I always travel with wood or bamboo needles. It takes long enough to go though security without having to stop and explain your knitting. The wood/ bamboo needles just don't show up on x ray. I carry a massive suply of needles I have a set of wood interchangeable needles and I carry tons of 0,1,2,3 sock needles.
If you have any doubts I always recommend carrying an extra set of needles in the same size in your checked baggage. Carry a plastic darning needle with some bulky yarn on it with your knitting project. Then if for any reason they try to confiscate your knitting you can thread all you live stitches on the needle and thread, and you have a back up set with you when you get to your final destination.
If you are on Ravelry there is a group called Plane-knitters who have been posting all the airports they have been in and out of and if they have had any problems.
I really hope this clears up any misconception that you can't bring needles on the plane. I love to see your projects! I usually have my camera and I love to post my fellow knitters projects!( I am still waiting for my new phone to get here....so still no pictures)
So I want to see lots of knitting on my flights!!!
Safe Flying and Happy Knitting