I have taken crochet hooks on planes several times.
Outbound, at Glasgow airport, both my crochet hook and my scissors (short blade, within the guidelines) went through security with no problems.
Same trip, on the way home, Heathrow security pulled me aside to search my handbag - turned out they wanted to check the scissors - I was allowed to take them on board once they had been checked.
Another trip, at security at London City Airport, the same scissors went through without a problem, but they pulled the crochet hook out and went into a little huddle to mutter about what the h ck it was.
Same hook and scissors each time - three different responses from three different security departments. In each case, though, I was allowed to take the crochet hook and scissors in the plane.