Flying units may move great distances and may cross enemy lands and Seas provinces as quickly as they cross friendly land provinces.

The flying ability doubles a unit's patrol strength and siege strength, making flying units particularly efficient for these roles.

Flying in combat costs some fatigue, which is increased by rain or snow from Rain and Storm.
Storm prevents flight, unless the flying unit has Storm Immunity.

Flying melee troops are usually scripted with Hold and Attack Rear to give time for enemy infantry to advance, leaving vulnerable archers and commanders exposed. In some battles, flyers scripted to attack immediately can be have a decisive role through interrupting the scripts of enemy mages or thugs.

With good leadership, it is possible to script flyers to advance on foot in combat. Flying units set on a Line or Double Line formation, and scripted to Attack, Fire, or Hold and Fire (not Hold and Attack!) will advance on foot, rather than flying, once they have exhausted any ammunition you told them to shoot. This can be useful both for flying infantry who you'd prefer to serve as a stable front line, and for flying archers like the Spire Horn Archer, who would otherwise bravely fly into melee with their Ice Knives when out of ammunition. This is not a panacea; the combat AI may decide to switch a squad in one of these formations to flying later in the battle.

Most flyers trade poorly with similar quality units, or even province defense, in a fair fight – but win by sniping the commanders, triggering an early rout. Supporting province defense with an extra commander positioned near the front, ideally with bodyguards, can be very effective against flyers raiding with Hold+Attack Rear.