At the risk of spoiling the joke, just curious about how powerful the drones will have to be...

https://www.tarpsplus.com/blue-poly-tarp-sold-individually.h...

"3.5 oz. Per Square Yrd."

  You have: 3 mi 4 mi 3.5 oz/yd^2
  You want: kg
   * 3688250.3

So each drone should be able to lift about a gigagram.

(Also, this plastic doesn't have enough tensile strength to support its own weight when lifted from the corners.)

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).

The standard approach, as was used in Iraq, is to dispense foil streamers or other conductive chaff over the substations. The US used airplanes, but these days drones could do the job. Or you could use a drone to tow a copper wire across one of the high-voltage distribution power lines. If done on enough lines at the same time the sudden decrease in load may cause the generators to overspeed.

The Weapon that Disabled Iraq’s Power Grid

https://cyberarms.wordpress.com/2010/04/28/the-weapon-that-d...

You need to delete this comment before the terrorists find out about this possibility.