Over the course of the game, you're going to encounter anti-air cannons that're going to be rather pesky when you're trying to fly around the map.
As well, tanks are relevant throughout the world, as they'll try and mow you down any chance they get. So, its your best bet to get familiar with some of the many ways we've discovered in Far Cry 6 that you'll be able to deploy in order to counter-act these enemies.
Near some of these anti-air cannons are Explosive Barrels that you'll be able to shoot and they'll instantly blow up, causing the cannons to be destroyed. As well, if you happen to get control of a tank, then this is an obvious route you can to get rid of these.
Furthermore, if you're looking to take down tanks, then we'd recommended using RPG's or a flurry of grenades. This will slowly chip away at the armor the tank has to offer and should blow it up eventually.