...That makes it sound like a job for the AC-130. It could fly high, for a long time, and carry not only a lot of PGMs but also large powerful radar systems to identify ground targets and track them.
Thing is, AC-130 is in the MANPADS engagement range, and IIRC one was lost in Desert Storm due the SA-7 or SA-14.
Only when it's taking off and landing, yes? SA-7 and SA-14 reach a maximum altitude of 2300 meters, and AC-130 has a service ceiling of 12000 meters.
That's service ceiling, not the altitude at which they provide fire support, which will vary depending on the conditions and threat.
Since Vietnam, AA threats have pushed gunships higher and higher, requiring more powerful ordnance to remain effective at the slant ranges involved, which is partially why things like 7.62 miniguns and 20mm gatling guns have disappeared, giving way to 25mm, 40mm and 105mm. The latest variant uses 30mm and 105mm. In 2007 a study was done regarding the potential use of 120mm mortar, guided rounds would increase the engagement envelope and allow the aircraft to operate higher.
Im sure I read somewhere they were even using repurposed copperhead rounds as a secondary weapon for Gunships, for just this reason. Dont know if it ever made into service, but it was certainly trialed.
Wasn't copperhead for 155 mm and the gunships carry 105 mm. Up gunning from 105 mm to 155 mm would be a huge amount of weight and recoil.