Cities: Skylines - Airports Review (Katyusha)
Ignore the bad reviews complaining about bugs; they've been fixed as far as I can tell. Yes, this DLC had serious issues at launch, but not anymore.
Airports is pretty much a "cosmetic" DLC that doesn't change anything about how your overall city functions, but it's a REALLY GOOD cosmetic DLC. It's a night-and-day improvement if you care about airplanes, because the vanilla airports are BAD. Real bad. And for a game so focused on transport, having bad airports is a pretty serious mark against it. Airports takes what was probably the ugliest, least realistic-looking, and most boring type of transport in the game and turns it into perhaps the most beautiful and engaging. Designing and detailing airports is really fun, and being able to custom design airports in a wide range of sizes and form factors makes it easy to fit realistic air transport into even the most cramped maps. It's also one of the better uses of Parklife-style areas, which seems like a weird way to implement airports until you realize that making the area also automatically smooths out the terrain, which is essential. The only real complaint I have is that Airports doesn't do anything to improve the Aviation Club from Sunset Harbor, which is really disappointing as a fan of general aviation. That, and there are almost no mods to improve Airports content or add compatible assets, but that's not CO's fault.