Air missions

Hearts of Iron IV

Air warfare

Aircraft

Air missions

Air combat

Air technology

Air doctrine

Air wings can be assigned to various missions. If no missions are assigned, air wings will remain idle in their air bases. Different missions are available for different plane types.

Mission efficiency

Strategic air view showing 62% mission efficiency in the strategic region.

Air base view showing red mission efficiency of the first air wing and yellow mission efficiency of the second air wing.

The mission efficiency of a wing influences what percentage of its planes can actually carry out the assigned missions. Note this is different from mission-specific modifiers like Air Superiority Mission Efficiency described below.
Mission efficiency in a strategic region is shown in the strategic air view window, that is shown if you click a strategic region in the strategic air map mode.
Mission efficiency of an air wing is shown in the air base view window, that is shown if you click the airfield in which the air wing is stationed.
Mission efficiency icon:

• Red icon means mission efficiency < 50%
• Yellow icon means mission efficiency >= 50% and < 100%
• Green icon means mission efficiency = 100%
• Icons with the clock symbol mean that the air wing recently arrived in the region and the mission efficiency is building up.

Effects on mission efficiency of an air wing:

• If the wing's range does not cover the entire strategic region, it will get a range penalty proportional to the provinces that are not covered.
• Airbase overcrowding causes a large penalty.
• Bad weather conditions reduce mission efficiency.
• Lack of fuel reduces mission efficiency.
• Wings newly assigned to a strategic region get a temporary, decaying penalty to mission efficiency.

Effects on mission efficiency in a strategic region:

• The mission efficiency of the strategic region is the weighted average of the mission efficiency of the air wings operating in the region.
• Assigning more ground crews in the strategic air map mode gives a +10% bonus to mission efficiency in the strategic region. This bonus is multiplicative.

Missions will be conducted regardless of weather, but bad weather reduces detection and efficiency and increases the risk of an accident at take-off and landing. The effects increase with weather severity, with sandstorms and blizzards being particularly bad. It may be advisable to put air wings on standby during such conditions.

For some mission types, there are modifiers improving their effectiveness which are also called "mission efficiency": Air Superiority Mission Efficiency, Interception Mission Efficiency, Air Support Mission Efficiency, and Naval Mission Efficiency. They improve the following stats of aircraft executing the respective mission type:

• Agility
• Air Attack
• Air Defense
• Naval Agility
• Naval Attack

Escort Efficiency belongs to the same family of modifiers but has no effect.

Pilot exercises mission

Available for: All planes, except rocket interceptors, transport planes and scout planes.

Pilot exercises can be used to gain experience for the air wing and to gain national air experience. You will consume fuel and increase the risk of air accidents while running pilot exercises.

Enabling pilot exercises will disable all other missions.

By holding the "shift"-key and clicking pilot exercises, the air wing will exercise until it reaches maximum training experience and then stop automatically. The automatically stop pilot exercises when fully trained icon will show when properly enabled.

Air superiority/escort mission

Available for: Fighter, Heavy Fighter, Jet Fighter

Wings with this mission will fight and disrupt any enemy air wings operating in the area. The air superiority mission doubles as escort mission, protecting bombers operating in the region by reducing disruption from enemy fighters.

Close air support mission

Available for: CAS, Tactical Bomber, Jet Tactical Bomber

Close air support, also known as air support or ground support, is the use of aircraft to assist troops in land combat. Wings with this mission will participate in land combat throughout the strategic region. Air support gives an attack bonus to friendly troops and also directly damages organization and strength of enemy divisions.

An air wing can support any land combat in provinces within its range. Combats close to its air base are prioritized as well as (to a lesser extent) battles with more divisions. The priority rating is excess air wing range (in map pixels) plus number of total division on both sides of the battle.

Number of CAS per battle

The maximum number of planes allowed to join a land battle is 3 times the used enemy frontage as a base value. The maximum allowed CAS in the battle is adjusted by the type of terrain in the province where the land battle takes place (see the "enemy air superiority" column). A wing with more planes than can join its highest priority battle can split to join multiple battles. The CAS frontage of a battle can be filled by planes from multiple friendly wings. Thus, there is no need to match CAS wing size with combat widths.

Example: A battle takes place in a forest province (-10% enemy air superiority). The enemy frontage (width of non-reserve divisions) is 20 which allows 3x20*(1-0.1) = 54 planes on CAS mission to join this battle. CAS wings will contribute planes to the battle up to 54 planes.

Attack bonus to friendly land units

CAS provide an attack bonus which boosts the stats of friendly units in the combat. The bonus has a base value of +25%, scaled linearly by the number of planes actually in the battle compared to the maximum possible. For example, in the earlier example with a maximum of 54 CAS, if 27 planes were in the battle, the attack bonus would be +12.5% (27 / 54 * 25%). With 48 CAS present, the bonus would be +22.2%. The air support bonus can be observed in the tooltips that appear when you hover over icons for land units stats shown in the battle display.

CAS damaging enemy units

The attacking planes deal ${\text{ground attack}}*{\text{number of planes}}$ attacks against a randomly selected enemy division. An ace can increase the amount of attacks, while weather might decrease it (stacking multiplicatively). The attacks are resolved as between land units, but they ignore defense, hardness and armor. A general can reduce the damage received with the "Damage Reduction Against CAS" modifier (Camouflage expert provides 50%). The resulting damage values against organization and strength are scaled by 0.04 instead of 0.053 organization and 0.05 strength as in land combat between divisions.

Enemy units damaging CAS

Divisional anti-air (AA) weapons reduce the damage from CAS. Anti-air capabilities are averaged across all divisions including the reserve. The maximum damage reduction of 75% is already achieved at 10.7 average anti-air attack.

Additionally, the divisional AA (again using the divisions' average) has a 7% chance to shoot down a portion of the attacking planes. When it does, it can shoot down a fraction of attacking planes up to 0.5% × (air attack). The actual amount is a random value up to that portion (i.e. on average half as much) but at least one plane always gets shot down. None of the plane's attributes have an influence on the effectiveness of anti-air.

Example: The enemy side of a battle has four divisions with 1936 support anti-air battalions (15.2 air attack) and four divisions without any anti-air. They get attacked by 91 CAS planes every 8 hours. The enemy side's average division air attack is $4*15.2/8=7.6$. Averaged over a long time, they will shoot down $91*50\%*7.6*0.5\%=1.729$ planes every time they are attacked. (Taking into account the minimum-of-1, the result is 1.84).

Air experience

Every plane that joins a battle produces 0.0005 country air experience.

Interception mission

Available for: Fighter, Heavy Fighter, Jet Fighter, Rocket Interceptor.

Wings with this mission will only participate in air combat if enemy bombers or transport planes are detected.

Strategic bombing mission

Available for: Strategic Bomber, Jet Strategic Bomber, Tactical Bomber, Jet Tactical Bomber.

Strategic bombing is the act of damaging enemy buildings, industry, and infrastructure via planes designed to drop bombs. Wings with this mission can prioritize the type of target (such as airbases, radar installations, forts, infrastructure, etc.) within the strategic region by clicking on the proper button. Note that your bombers may get targeted by State anti-air . Strategic bombing damage is about 120 damage per attack cycle for ~0.3 buildings destroyed. This damage appears to be distributed among all the targeted buildings (forts, industry, etc.) in the air region without regard to the number of air wings present. World War II bombers were inaccurate, and therefore the amount of bomb damage varies greatly from day to day.

Players carrying out strategic bombing should note:

• Strategic bombers are very expensive to construct and in many cases a significant number are required to have any meaningful impact. Carefully consider the opportunity cost of committing many factories to a strategic bombing campaign.
• If the enemy air region is heavily defended with fighters, the bombers may need to be escorted. Only heavy fighters have enough range to escort strategic bombers deep into enemy territory, but they can be beaten by light fighters.

Players subject to strategic bombing can respond in several ways:

• State anti-air emplacements (built in the Construction interface or States view) will not only destroy the enemy's bombers, but they will also receive some of the bombs (diverting them from the factories, refineries, resources, and naval facilities that the defender needs to protect).
• Strategic bombers can be fought in the air by fighters. Heavy fighters are more effective than light fighters in this role. Bombers are much slower and less agile than fighters, so players designing defensive fighters will find guns are most effective. Heavy fighters' larger range also means that they can be used to defend a larger area.
• The Construction Repair Continuous focus will speed up the repair of damaged buildings. This will help the region to recover.

Players can assess the impact of their bombing and their defenses in the region's air combat screen (number of buildings bombed, percentage of bombers disrupted). The details pane of that window provides numbers across a long time frame.

Naval strike mission

Available for: Naval Bomber, CAS, Tactical Bomber, Jet Tactical Bomber

Wings with this mission target enemy ships, both inside and outside of naval battles. They may get targeted by naval anti-air. Air wings have a base 4% chance to detect or find an enemy fleet. This detection percentage is modified by other variables.

Once an enemy fleet is discovered, a randomly assigned ratio of planes to fleet frontage is determined. Fleet frontage is calculated from the total hit points (HP or health) of the enemy fleet divided by 20. Typically, the ratio of attacking planes to fleet frontage is 1:1. Each plane assigned to the attack rolls to hit a target. If the plane from carrier hits, it does damage equal to the plane's naval attack (naval damage) value. And if the plane is from air base, it does damage equal to the one fifth of plane's naval attack value. In a fleet with multiple ships, the target is randomly selected (note: increased ship's surface visibility may increase its chance to be selected as a target...more visible targets are more often struck. This needs to be verified). For example, if a NAV1 hits a heavy cruiser 1, the NAV1 will do 1.5 points of damage. That is, the battleship will lose 1.5 hit points out of its total of 150 hit points.

Naval strikes using only airpower never attack enemy convoys carrying resources or supplies. They can attack enemy convoys carrying troops. However, convoys auto-repair between each attack, and most aircraft are too weak to sink a convoy in one attack. Only NAV2 and NAV3 have a sufficiently high naval attack value to sink troops convoys. The auto-repair mechanism also means that bigger wings are better.

The situation is quite different if naval strikes are combined with an attack by warships (including submarines). In this case, the resource and supply convoys can also be the target of an attack, and many different types of aircraft can be useful (i.e., not only NAV2 and NAV3).

Kamikaze strike mission

Available for: Fighter (needs to be unlocked by country rule)

This mission is equivalent to the naval strike mission, but with increased effectiveness and losses.

Port strike mission

Available for: Naval Bomber, CAS, Tactical Bomber, Jet Tactical Bomber

A port strike mission is an air attack against enemy ships located in a naval base. Naval bases are located within provinces on land, therefore, port strikes can only take place in a region which covers land. The naval base itself will get damaged as well during successful attacks, but empty bases cannot get attacked.

At least 30% air superiority is required to perform port strikes . The number of airplanes involved in a port strike is increased by the port strike value (e.g. 50% more aircraft are involved in a port strike if you have the first "Base Strike" naval doctrine). Note that air wings on a port strike mission may get targeted by state-level "static" anti-air .

Logistics strike mission

Available for: CAS, Tactical Bomber, Jet Tactical Bomber

A logistics strike mission is an air attack against enemy trucks, trains and railways.

Air supply mission

Available for: Transport plane

Wings with this mission provide supply to assigned ground troops if land-based supply is insufficient. Command points are automatically used for these missions and and costs permanent 0.3 command power while mission is active. Transport planes can be shot down while on the mission, both by enemy fighters on interception missions and by state anti-air .

Each plane can give up to 0.2 supplies, meaning a full wing of 100 can give 20 supply. This amount is affected by mission efficiency, so lacking air superiority or range to reach the whole area will result in less supply getting through, while using More Ground Crews will slightly increase the amount. The supply given by this is used to make up supply deficits in the assigned strategic region, meaning that only units that don't receive sufficient supplies from normal sources will receive air supply. If no units have a supply deficit in the region, the mission doesn't do anything, but the planes will still consume fuel and possibly get shot down.

Naval minelaying mission

Available for: Naval Bomber, Tactical Bomber, Jet Tactical Bomber, Strategic Bomber, Jet Strategic Bomber

The technology, Aerial Minelaying, must be researched before aircraft will become capable of air dropping naval mines.

Planes capable of naval minelaying can be assigned to naval minelaying missions only during wartime. These planes will continue to air drop mines to the assigned strategic region until 1000 mines have been laid in the region, at which point the region is considered to be fully saturated with mines.

The rate of minelaying depends upon both the quantity and type of plane which make up part of the air wings assigned to a region.

As mines are laid, some mines will graphically become visible on the map. While either the strategic air or navy map mode is selected, hovering the cursor over a region containing mines will show the number of mines that have been laid, along with the number of enemy ships damaged or sunk by the mines.

Base minelaying efficiency by plane type

• 5% Naval Bombers.
• 8% Tactical Bombers.
• 8% Jet Tactical Bombers.
• 13% Strategic Bombers.
• 13% Jet Strategic Bombers.

Effects of mines

The following effects apply to each mined strategic region, scaled according to the quantity of mines:

• Increased naval supremacy for the owner of the mines.
• Increased chance of accidents and decreased speed for enemy ships. (These penalties do not apply to friendly ships.)

Naval minesweeping mission

Available for: Naval Bomber, Tactical Bomber, Jet Tactical Bomber

The technology, Aerial Minesweeping, must be researched before aircraft will become capable of detecting and neutralizing enemy naval mines. Planes capable of naval minesweeping can be assigned to naval minesweeping missions during wartime. These planes will continue removing mines from their assigned strategic region until the region is fully clear of mines.

The rate of mine clearing depends upon both the quantity and type of plane which make up part of the air wings assigned to a region.

Base minesweeping efficiency by plane type

• 10% Naval Bombers.
• 15% Tactical Bombers.
• 15% Jet Tactical Bombers.

Air recon mission

Available for: Scout Planes

Scout Planes on this mission perform aerial scouting and intel gathering, adding additional intel to the total intel from all sources on the countries in the target air zone. The increased numbers are shown in the Intel Ledger in the Diplomacy screen for a country.

Intel cap

The amount of intel that scout planes can contribute to the overall intel about a nation is capped. Scout planes can only contribute up to 20-30% of intel in a given area. Scout planes can continue to accumulate intel up to 5% points above this cap, however, this intel in excess of the cap doesn't contribute to intel against that nation. The excess intel only serves as a buffer if the player stops performing any air reconnaissance. The excess intel will begin to tick down, and only when it falls below the effective cap will the player begin to lose effective intel against that nation.

The effective and hard cap that scout planes can contribute to intel are

• Civilian Intel: Effective cap 25% (Hard cap 30%)
• Army Intel: Effective cap 20% (Hard cap 25%)
• Navy Intel: Effective cap 30% (Hard cap 35%)
• Air Intel: Effective cap 20% (Hard cap 25%)

Rate of intelligence gathering

To gather intel % on the industry/army/air of the country, the Scout planes can be assigned to any air zone and build up the intel bonus (to the intel tabs) over time. The more planes you fly over a state, the faster you will reach the maximum. How quickly you build intel isn't clear, but adding more scout planes to an air wing reliably increases the rate at which intel is generated.

Air superiority

If you place a Scout plane inside an air zone with combats, they will contribute towards air superiority bonus, even though they will do no damage to air units nor ground/naval targets. Intel advantage + air superiority can go from 25% to 40% bonus. In a Naval zone, the Scout planes will contribute towards air superiority in the zone which increases detection in the Naval zone.

Example below: As the UK player, there is 60% intel about Italy's air force. 2% comes from radar. 28% comes from the spy network (2 agents in Italy). 20% is from air recon (scout planes) and 10% is because of their fascist ideology.

Intel screen showing effect of Scout planes

Naval patrol mission

Available for: Scout Planes

Scout Planes on this mission perform aerial scouting in the target sea zone without engaging enemy ships. These planes help friendly task forces patrolling the sea zone to spot enemies.

Multiple missions

Wings with multiple assigned missions will fly exactly one of the selected mission types per mission opportunity. The mission flown will be the first one in priority order, as shown in the left-to-right order of the buttons in the air UI. Mission efficiency bonuses (e.g. from air doctrines) only for that mission type get applied to the wing for that mission.

To perform multiple missions simultaneously, create multiple smaller wings and assign a wing to each individual mission.

Most missions are conditional, in that planes will only fly if there is a known target at the time a wing mission is being chosen. Some missions will always fly. Targets are checked in each of the air zones assigned to the air wing, checking provinces within range of the air wing. If there are no appropriate targets for a mission type, the mission selection process will continue to the next lower priority mission. The first mission with a valid condition is the only mission flown by that air wing during that mission opportunity. Since many of the conditions during play are dynamic, wings may fly different missions at different types, producing multiple types of results. If one of the assigned missions has a condition that's "Always executes", no later mission in the list will ever be executed by that wing.

In the table below, determine the mission that will be flown by a wing with multiple missions selected by reading the missions from the first line downwards, stopping at the first mission where the condition is true.

Mission Execution Priority

Mission	Condition
Pilot Exercises	Always executes
Air Superiority	Always executes
Close Air Support	Ground battles are in progress
Interception	Enemy bombers are detected in an assigned air zone
Strategic Bombing	At least one undamaged building, including state buildings in partially covered states (if any)
Naval Strike	Enemy ships are detected
Kamikaze Strike	Enemy ships are detected
Port Strike	Enemy task force in port
Logistics Strike	Enemy divisions or air wings are receiving supply from a supply node
Air Supply	At least one friendly division with a non-zero supply consumption is present
Naval Minelaying	Always executes
Naval Minesweeping	Always executes
Air Recon	Always executes

Warfare