S.A.S.

The Siege Aerostat is an aerostat, not a bloon. It looks like a green M.O.A.B. without a tail rotor. It fires brown bloons at your towers, but they don't do any damage, and they only serve to create a diversion, so that your towers attack the brown bloons, not what's supposed to be coming. If it is destroyed, it drops a cargo of three brown bloons on the spot where it was pushed on screen.