Airplanes are a special kind of troops in your battle group. Aircraft units may not occupy land or take strategic points. These are support units and air superiority units. For this second purpose, fighters and heavy capture fighters are being used. Bombers can replace artillery units. You can bomb any place on the map unless there is some anti-aircraft artillery. There are many different types of bombers, where each has their own destination and works best in a given situation.
Although you buy planes in the same way as the other units, you summon such units from off the map. Most units will circulate around the battlefield until the fuel reserves are exhausted. Bombers leave the mission area after the bombardment of a designated location. Airplanes can retreat if they are under heavy enemy fire (their morale will be suppressed in the same way as in ground units). If the aircraft is damaged, it will stay off the map longer after evacuation until the repairs are completed.
It's the airborne version of the reconnaissance troops. It's a slow and cheap plane, usually unarmed. However, it provides a lot of information about the movements of enemy troops. As this is an airplane, the enemy without anti-aircraft weapons cannot harm it. Therefore, it is an ideal reconnaissance unit for the first phase of the game or for a division without air support. You can easily track an enemy army or ambush incoming enemies, detect an artillery position and eliminate them with your own artillery.
Their main task is to bomb the enemy's position. Pay attention to the size of the air bombs they have on board - the greater the weight, the greater the explosion, but fewer bombs will be transported on board the aircraft. Small bombs in large numbers are great weapons against infantry and other minor troops, and large bombs such as 500 or 1000 kg are used to destroy fortified enemy points and other static objects - these are even used to destroy tanks that are immobilized. Some bombers have napalm to destroy enemy infantry in a large area or to suppress the morale of units. Other bombers have AP cluster bombs, which are mainly suitable for use against armored units.
You must remember that once you have assigned an enemy unit to your target, your plane will drop bombs on the specific position, even if enemy disappears from sight. Then the bombs will be dropped on the last known position. Sometimes this feature is very useful because enemy troops quite often don't change their location. In other situations it will be better if you stop your attack or point to another target (in case of shooting at a fast enemy unit). Also, you can bomb a column of trucks or tanks, but you have to do two things to make the attack successful: at first, set the bomber to fly in the same direction as the incoming enemy column. It is best to choose a long way of the path, if the enemy column suddenly change its route. Secondly, you need to select the first vehicle as the target. The bombs won't hit the front of the army's column, but they'll explode on the other vehicles. Such an attack requires micro-management, but it is very effective.
Fighter, Heavy Fighter
These are the air superiority units. Their main task is to fight all enemy's planes. Fighters are great in combat with small enemy airplanes, that means with other fighters, reconnaissance aircraft, small bombers, etc. Heavy fighters, however, have strong weapons, but are slower and less maneuverable. Their task is to destroy slow enemy machines, like large bombers. If there are no air targets, fighters can boldly attack ground targets, mainly cause some heavy trouble to infantry. Usually they don't cause much damage, but they do cause a lot of confusion and quite well suppress the morale of enemy units.
Ground Attack, Tank Buster
In this category you can find planes of different sizes with light and strong weapons. These are mainly machine guns and cannons of various caliber, rockets and cluster bombs. The purpose of these machines is to pin down the enemy, especially some minor units such as infantry. Tank Buster class of planes are specialized machines which main purpose is to attack and destroy armored units - one of the iconic machines of this type is the German JU 87 G with powerful 37 mm cannons. It can easily destroy most tanks as these have weaker upper armor. Cannons have a limited amount of ammunition, but they're very accurate and effective.
Many planes with AP rockets can destroy even small groups of armored vehicles, while HP rockets can perfectly suppress the morale of such vehicles. Obviously, the latter type is extremely effective against infantry troops. Disadvantage of such planes is very limited amount of ammunition - after the attack planes evacuate immediately. Unlike rocket-powered machines, Close-Air Support planes endure much longer on the battlefield, but usually have machine guns that are mainly used to harass light units such as infantry, trucks and artillery.