@mkgionet
An Industrial Complex must be transformed to an Underground Factory at least one round before it can be destroyed by the owner.
An Underground Factory can be destroyed by the owner at no cost - it is simply removed from play.
See page 20 for further details.
Concerning Strategic & Tactical Bombing and Air-To-Air Combat Over Target Area:
In your example, there are no Strategic Bomber units. So I assume that you are conducting a Tactical Bombing Raid against an Air or Naval Base.
In your example, during Air-To-Air Combat Over Target Area all attacking air units attack at “3” - and defending fighter units defend at “4”.
Once the Air-To-Air Combat Over Target Area has ended, the Tactical Bombers (if any survived) are exposed to AAA by the facility that they attack.
There after, any surviving Tactical Bomber unit can drop its bombs on that facility.
See page 23 and 24 for further details.
Remember:
Strategic Bombing Raid: During Air-To-Air Combat Over Target Area any Strategic Bomber unit defends at “1” against the Fighter units that protect the Industrial Complex (Target).
Attacking Heavy Bomber units each defends with 2 dice at “1”.