I had in mind birdshot CIWS mounted on top of a truck that could tear ass around the airport. Even if you could only place one or two in a fixed location, putt

I had in mind birdshot CIWS mounted on top of a truck that could tear ass around the airport. Even if you could only place one or two in a fixed location, putting them next to tempting targets for invading drones looking to taunt the airport, such as the control tower, would probably work pretty well. Consider that the invading drone will only succeed in shutting down the airport if somebody notices it; somebody trying to commit economic sabotage will be making the presence of their drone known. If the invading drone goes unnoticed, then it will fail to accomplish it's mission. As for drones flying too high, that is a problem but one that could be addressed (not solved) by using interceptor drones to spook or bait the invading drone into flying lower. On a non-ballistic sidenote, you could also have race quads configured to rapidly triangulate the origin control signal and collect video evidence of the signal origin. Not fool-proof by any means, but I wager that would be enough to catch all but the most clever/dedicated attackers. This all seems a bit silly, but if you throw enough money at it I think you can make it work. The question is how much economic harm can a drone do by shutting down an international airport and how much money are you willing to spend to prevent this. My main point here is that the situation isn't nearly as hopeless as a bunch of soldiers taking potshots at the drones with their rifles (that's pretty much guaranteed to be not work and is exceptionally dangerous.)