This question comes up pretty often in my knitting classes... usually around the time that I mention that socks are ideal travel knitting.
Yes, travel. As in planes.
I've never had a problem with plastic, bamboo and wood needles either going through security or on the plane. No one has ever stopped me. I have successfully traveled with a circular metal needle, too, but I went prepared to have it confiscated -- it was a lace project, and a lifeline had been threaded so it didn't matter if I had to remove it from the knitting. No problem, and it went back and forth to New York with me a couple of times.
The trick seems to be to not ask. You say the word needle to the poor security guard and he/she is more likely to think of something medical than craft-related. So I just put 'em in my carry-on bag and send 'em through the x-ray machine.
This worked again for this most recent trip.
But I did encounter a new resistance. I was asked by the flight attendant to put the needles away for landing.
I suppose I could have hurt myself with them in a landing incident... should I take away from this that knitting in the car is dangerous, too?
Hey, we all gotta take risks....