Flying units -- what is their use?

[PvK]

If you have a flying fighter/commander, you can give more detailed orders to their flying troops by giving those troops guard commander. So you then can give the commander something like Hold Hold Hold, Attack Rear, Retreat, and the whole group, or five holds and then attack, or whatever you want, and the whole group will follow the commander. There are still limits though, and Retreat, while it gets the fliers out of there - it also randomly scatters them over the available adjacent friendly provinces, which would generally be obnoxious (though if you have cheapo mop-up gathering commanders, it can be ok). Of course, if your fliers are strong enough, they can be the decisive strike, rather than a harrassing force.

The point about strategic movement is also very important. They can fly over enemy provinces and armies, and can attack provinces they aren't adjacent to.

PvK