[HillaryBriss]

Good point! The plan needs refinement.

I guess they could break the job down: use one team of 4 drones to lift multiple 1 square yard tarps.

Let's see, 12 square miles is roughly 37 million square yards. Multiplying by four they would only need about 150 million drones. Quite affordable for today's well-funded terrorist with an Amazon Prime account (as long as they choose 3-5 business day shipping instead of overnight).