It frankly doesn't sound overly compelling.
Sure, a drone falling down could potentially crash into something and cause damage. It could crash into something really expensive (like an airplane). A bullet could cause damage to something (actually, shooting at a very steep angle, the point where the bullet returns to the ground could be reasonably constrained).
Except - compare this with the cost of closing an airport for 36 hours and grounding the passengers, causing canceled business meetings and all the shbang etc. I have a hunch the latter is quite a bit more.
Also, a fairly obvious idea would be a *really large* drone operated by airport security with a net underneath... Sure, it's probably expensive to have something like that on standby and a trained crew.
But... compare with the cost of closing an airport for 36 hours...