Most fighters don't cruise around on full AB; they cruise at lower throttle settings to conserve fuel.

So again, how are you going to get these 100k ball bearings up to 20k AGI? Your slow, cheap drones are just going to loiter up there and hope an F-35 flies into their web?

It's not like the air forces of the worlds would be ignorant of this "surprise" tactic. And the methodology of targeting an F-35 with a cascade of ball bearings is conveniently left out of your scenario.