"Thats all very nice but what if drones go into each of the engines? A long shot I know but for a serious attack a 'cluster' of drones could be launched."
I suspect that even under ideal conditions, targeting a jet engine intake with any sense of reliability is going to be TOUGH. Doing it to two simultaneously will be near as dammit impossible.
Consider. Working in 3D space at distance enough that your drone(s) are mere specks aiming for a target maybe about 10' diameter (and also little more than a speck) with no background reference objects for ranging or perspective and said target is moving at 200+knots.