My experience has been that no matter what the airline-- or even the airport!-- tells you, that you are at the mercy of whomever happens to be manning the security check point at that moment. The TSA says that they are allowed, but some security people won't let you through with them, and then you're stuck and probably have to throw them away. So I say, unless they're cheap-you-don't-care needles, don't try it. I know how horrible it is to be on long flights without knitting
! But I think better safe than sorry on this one.