I'm sure that there are smart, experienced people thinking about this: how hard would it be for someone to put a bunch of explosives onto a drone and fly it into the engine of a plane that's just rotated from takeoff, or is lining up for touchdown? I don't imagine it would be easy, but can it be done at all?I have to believe yes. Drones with video downlink exist now; drones that can carry payloads, ditto.
So I find myself wondering: If I had to defend against something like that, what would I propose? A sturdier airplane? Bang goes fuel economy, up go air fares. An active defense system? I don't think even military aircraft have the ability to detect something that small, closing that fast, so I doubt commercial aircraft will, any time soon. Some kind of jammer to interrupt targeting signals? That might work -- at least, until drones with autonomous guidance, flying based on pattern recognition, come into play.
So, what can be done? And who's doing it?