As I'm trying to move up to immortal, I find my games are going later into the tech tree, and I'm seeing more air units in cities that I'm attacking. Up until now, I haven't had any use for any air units other than airships, which I find to be somewhat useful in defense. I'd be interested in what strategies advanced players use with respect to air units. Are there good combinations/uses that aid war strategies that people use? I tend to continue to default to my usual stack composition, which is cannons/rifles cavalry until the late game, and then infantry/artillery, with some tank and anti-tank support once the AI hits industrialism. I'm wondering if there's a reason to divert to pick up flight and other air-related techs to maximize the use of air power in my late game wars.