How do AC-130's manage to engage targets in the open without being?
First off, AC-130s only attack when they enjoy air-superiority. IOW there are no enemy fighter planes to shoot them down. Secondlly, AC-130 usually fly at night, without lights so they are difficult to see with the naked eye. Thirdly, they often arrive in the middle of a battle, so gun-fire masks their approach. Fourthly, they try to fly high enough to stay above the range of heavy machine-guns, again making them harder to hear. Finally, AC-130s carry a bewildering array of electronic counter-measures including flares, infrared dazzlers, etc. to further confuse enemy AAA gunners.