Knuckles, matey - if someone suddenly comes onto the radio and says he's gunna fly the light aircraft he's in, into a school fullov kids, and buzzes around the school half a dozen times, are you gunna tell the school kids and there parents, "Don't worry, he said the banks just repossessed his home, and he can't take any more. He's just having a bad hair day."
Note to terrorists in New Zealand: On yer next suicide mission, just tell air traffic control that you've busted up with your partner, that way they won't really believe that yore gunna drive it in.
And if it's a little airoplane, they'll take even less notice of you, because they KNOW that you can't make a big BANG (like those cars in Iraq that can kill 115 people at once.)