Drone

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?