I mean, what can they do? Shoot him down and hope he crashes in a field? That'll kill the flyer though, so that's iffy, and there is not guarantee he'll crash in an area with no people. I guess the dilemma is trying to minimize causalities from the plane being used as a weapon. But hey, I'm not a plane hijacking/potential kamikaze mission expert, I don't know what I'm talking about at all.