AccursedTheory said:
Everyone seems to have been stuck into WWII (And there's a reason for that, it was the classy period for aircraft and featured the most variety and character), so here's something a little younger.
The Fairchild A-10 Thunderbolt II, more commonly known as the Warthog due to its distinctive paint job, is a plane so massively ugly it loops back around to looking good again. Designed and deployed during the time before cheap, effective guided missiles made close air support planes obsolete, the A-10 is a one of a kind design - Able to take more damage then most armored land vehicles and still function, built around a massive 30mm Gatling gun that's still terrifying to this day, and loaded with enough rockets to take on God himself and arguably come out on top, the A-10 looks good, takes hits like a champ, and brought smiles to US infantrymen everywhere.
The A-10 also has the distinction of being the ultimate of its kind, most likely in a very literal sense. The niche it fulfilled has been made obsolete by other technologies, but it is still superlatively good at it. Like tank destroyers or battleships, we are unlikely to see their like again, so it'll remain the best there was.
OTOH, there is something to be said about dedicated CAS planes for low intensity conflict operations, but these tend to be cheap civilian aircraft with gunpods, that often wouldn't be too out of place during WW2. A much better CAS plane than not having a CAS plane, but made with cost in mind.
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I like the idea of the AC130, in that you take an ordinary transport with a large cargo capacity, and fill that space up with artillery.