Forgive my ignorance. I thought the AC-130 was starting to fill more of the A-10 roles given a lack of enemy fighter aircraft in recent conflicts and the desire to carry more armaments.
Quoting my own comment from another subtree below. AC-130s circle low and slow, and cannot maneuver quickly, which makes them very very good SAM targets.
After an AC-130 was shot down in Iraq, they only fly at night.
