Anti-Air



"We don't fly and we're not letting anyone else, either."

- Unofficial motto of Russian anti-air corps

Fighting against flying enemies is a pain when your own two feet are on the ground. Either your enemies can swoop down at you swiftly or stay high enough that your attacks cannot reach them.

For this situation, you need Anti Air: an attack, weapon, munition, ability, etc. that is effective against flying enemies. Alternatively, it can be something that brings the flying enemy down to ground and prevents them from flying again temporarily.

Works with flying monsters bring Anti Air to the fore. There's nothing like a dragon overhead to start a craze for archery. Effective Anti Air attacks are great for dramatic reversals of fortune in a story, with a flying enemy brought figuratively and literally low.

In games, one common way to add tactical depth and Competitive Balance is to make AA units excel against flyers, but fail against everything else—what we call Crippling Overspecialization. They usually form part of a Tactical Rock-Paper-Scissors game mechanic. For example, AA is great vs aircraft, aircraft are great vs troops, troops are great vs AA. Any unit not specifically devoted to the role will be unable to touch airborne enemies.

More generally, works set around WWII have given us a legacy of visual tropes: a sweating crew frantically traversing a multi-barrel anti-aircraft gun, the rapid pounding of the barrels, the terrifyingly fast blur of strafing aircraft. In works set from the pilot's point of view we have the sinister black puffs of flack appearing in the air all around them.

Specific anti-aircraft weapons are deployed in Real Life. However, units with mixed roles are more common than in games. For example, most warships have some sort of AA as well as their main weapons, or their AA missiles are their main weapons. Another difference of the Real Life AA weapons is that they most emphatically are NOT suffering from Crippling Overspecialization like their game counterparts.

These missiles often come in handy against lightly-armored surface targets, and, likewise, land-based mobile AA guns are usually not designed for frontline combat but they are damn great automatic weapons if push comes to shove, and are often employed as the antipersonnel defense. Contrast Point Defenseless. See also the Anti-Air entry under Air-Launched Weapons.

Sub-Trope of Weapon of X-Slaying. Compare Shoryuken for fictional martial-arts moves designed to counter an airborne opponent.

Anime and Manga

 * New Dominion Tank Police has an ironically accidental example of this when Leona Ozaki fires a prolonged burst from Bonaparte's minigun in frustration when the villains escape her which, unbeknown to her at the time, damages the villains' plane and causes it to explode moments later.
 * Ghost in the Shell: Stand Alone Complex: 2nd Gig has Kuze and several of his comrades using Stinger missiles to shoot down a JSDF jammer plane that had been disrupting all communications in Dejima.
 * In the Gundam metaseries, most MS carriers use vulcans or laser guns as anti-aircraft defense. Probably the clearest illustration comes in Gundam Seed Destiny, where the Minerva's CIWS shreds a Murasame rather viscerally.

Card Games

 * In Magic: The Gathering, Green magic, being the opposing school of Blue magic (which is fond of flying monsters), has several ways to specifically deal with flyers. These range from spells that damage or destroys all flying creatures or simply strips them of their Flying attribute, to creatures who could block flying creatures or could be tapped to deal direct damage to them.
 * Almost all Spider creatures had the ability to block flying creatures.

Comic Books

 * In one Punisher story where Frank infiltrates a Russian nuclear missile silo along with a Special Forces guy, they are trapped in a hangar with only an immobilized tank for defense. So Frank gets behind the machine and mows down the attackers, noting that the gun was originally intended for use against aircraft.
 * Wallace form the Sin City story Hell and Back is menaced by a Black Helicopter. Luckily, he has an old army buddy with an anti-aircraft missile launcher.

Film

 * Behind Enemy Lines has a rather memorable scene where the protagonists' plane is engaged by not one but two enemy surface to air missiles which are virtually impossible to outmaneuver or foil with any countermeasure they can think of.
 * Flight of the Intruder has North Vietnamese anti-aircraft defenses as a major and constant threat to the protagonists, which makes sense given the role of the titular aircraft as a low-altitude attack plane vulnerable to everything from advanced surface to air missiles to (literally) a peasant with a rifle. A major plot point in the film involves the protagonists going rogue to take out a stockpile of Vietnamese SAM's that were off-limits due to operational restrictions at the time.
 * The original book had them hitting the HQ of North Vietnamese Intelligence instead.
 * The Sum of All Fears shows the USS John C. Stennis aircraft carrier attempting to defend herself from a missile attack using a Phalanx CIWS turret, though it doesn't turn out very well.
 * It should be noted that in Real Life, the carrier would have been protected by the numerous AEGIS cruisers and destoryers surrounding it. Given that they were in range of a Russian bomber regiment, not having a CAP is also rather foolish.
 * The Death Star Turrets in Star Wars: A New Hope.
 * Which didn't work, since the Turbolaser batteries were intended for capital (Star-Destroyer caliber) starships, not one-man fighters. Plan B? TIE Fighter squadrons.
 * And then in The Empire Strikes Back, Hoth base has an anti-orbital ion cannon.
 * The Mechs in The Matrix sequels.
 * A major drive in Charlie Wilsons War is the need to find a weapon the Afghans can use to shoot down Soviet Hind gunships, which are armoured against anything up to .50 calibre. It turns out to be the Stinger AA missile.
 * Red Dawn has both the Russians and the Wolverines trying to invoke this trope against attacking helicopters. In the beginning of the film, we see a US Army Huey strafing the Russian forces (and exacting a Gunship Rescue for the heroes at one point), while the climax of the film shows the heroes take a desperate shot at a Soviet chopper with a rocket propelled grenade, hit it... and barely cause any damage at all.
 * Actually, the shot against the Soviet chopper was a perfect center-mass shot that went through an open hatch on the helicopter. The round would have continued going if it hadn't hit a crewmember.

Literature

 * Ecotopia. When the the fledgling title country was invaded by the U.S., its armed forces used missiles that deployed streamers to tangle up the blades of attacking U.S. helicopters. Which would work about as well as a chocolate flamethrower, but hey.
 * In the James Bond novel Diamonds are Forever, Bond uses an Bofors anti-aircraft gun to shoot down Jack Spang's helicopter.
 * Star Wars Expanded Universe:
 * In Isard's Revenge, Corran's X-Wing is seriously damaged by a stormtrooper using a shoulder-fired missile. Corran manages to make an emergency landing.
 * Like the Echo Base ion cannon in The Empire Strikes Back, planetary turbolasers are surface-to-orbit Wave Motion Guns. In this case, they don't disable Star Destroyers. They blow them to flinders (one volley is enough to destroy an Imperial-class).

Live Action TV

 * Stinger missiles are widely used by the Tau'ri in the Stargate Verse against enemy fighters. By Stargate Universe, they've added 200-round-per-minute railgun artillery to the mix.
 * In Stargate SG-1, Jack O'Neill once used a Colt M203 Grenade Launcher to shoot down a Death Glider.

Tabletop RPG

 * Champions supplement Gadgets!.
 * The Flight Neutralizer Gun took various forms depending on what type of flight was to be targeted. A net gun would tangle up wings, the "Gumball Special" plugged up jetpacks, heavy gravity models brought flyers down to earth, and an energy neutralizer stopped those who flew by an act of will.
 * The "Puff" ground to air missile deployed Kevlar streamers which snagged and fouled the propellers of prop-driven aircraft. Probably inspired by the Ecotopia example in Literature.
 * The "Theater Air Defense" unit in GURPS: Mass Combat has a strength of 50000 at TL 7 which makes it the most powerful unit in the game, capable of neutralizing the massively powerful Flying Battleship and and entire airforce at the same time.
 * In Warhammer 40,000, Hydra anti-aircraft tanks fill this role for the Imperial Guard with a quadruple-barrel autocannon. In a bit of a subversion, not only does it have a hull-mounted heavy bolter for defence, the barrels of its main armament can also traverse low enough to make mincemeat of enemy infantry and light vehicles.

Every race has anti-air units. The Space Marines use the Hunter, a tracked missile launcher, the Orks use the Flakwagon, which is an Orky copy of the aforementioned Imperial Guard Hydra, Eldar use Firestorms, hovertanks fitted with long-range scatter lasers, Tau use Skyray missile-armed hovertanks, and the Necrons use their Heavy Destroyers. All of these units avert the Crippling Overspecialization problem by being equally strong (the Skyray, not so much) against ground-based targets. The Hydra in particular finds that enemy hovercraft, which move very fast in three dimensions, behave similarly enough to aircraft that the Hydra shreds both with equal ease.
 * BattleTech - Fighters are a genuine threat to ground units of all kinds. So armies feild air defense tanks as well as anti-air 'Mechs, most of which can be identified quickly by a quad-barrel type arrangement. While most use traditional high explosive shells, some will use lasers instead, these being obviously able to do away with the bothersome trajectory issues of ballistics. Anti-air tank examples include the Partisan and Quad Panzer. Notable anti-air 'Mechs include the Jagermech and Rifleman.

According to the game's rules, LB-X autocannons can be used in an anti-air role, as their fragmenting rounds gain a to-hit bonus against aircraft. This becomes especially useful against any helicopters that make the mistake of sticking around too long.

Toys

 * Bionicle: the Venom Flyer's Rhotuka prevents targets from flying, naturally or mechanically.

Video Games

 * Witches in Dungeon Fighter Online can both jump three times AND dash through the air, and since no other class can do this, witches can be a real pain to fight (at least until they got nerfed). The only real effective class against witches are melee Exorcists. As they swing their axe or scythe, the weapon is so big, that when swung upwards for an uppercut, they can easily knock out midair witches (unless they are at the very peak of their jump, or used leap, etc.), much to their fear. As a side note, melee Exorcists won't flinch in the middle of the majority of their attacks, so Exorcists are as hard to approach as Witches are hard to chase.
 * Mechwarrior Living Legends has the Huitzilopitchli and Partisan anti-air tanks. They spew out hilarious amounts of ammunition at anything that flies, and are surprisingly effective against infantry.
 * The third Sly Cooper game has a mission during the final level where the player is tasked with eliminating the Big Bad's anti-air defenses which consist of automated missile turrets.
 * Master of Magic has the "Web" spell in the Nature Magic category, which momentarily immobilizes pretty much any unit. When used against flying enemies, even once they chop their way free of the web strands and can move again, web remnants prevent them from flying again, and they are ground-bound for the rest of the combat.
 * Standard to any Tower Defense is the Anti-Air tower, which rapidly destroys air units—but only air units.
 * Most RTSes with ground and air defense as separate buildings use the same principle: Anti-Air does more damage than a tower, and may have other effects such as splash damage, rapid fire. But AA units provide no defense against ground units.

Plants vs. Zombies partially avoids the above. The Cactus, which can shoot down Balloon Zombies, can still damage ground units as well. The Cattail can hit any zombie anywhere in the field, airborne or not. Only the Blover is highly specialized to deal with air units, and it still has the secondary effect of temporarily removing mist.

But in a strange twist, the Blover's overspecialization actually cripples the CACTUS too. Balloon Zombies are so rare that it is usually not worth planting a Cactus in each lane to guarantee that you pop their balloons. Blovers are less cost efficient, but you can plant Repeaters or something else with more firepower/other uses instead of the Cactus to use the spaces more efficiently instead. Not to mention that you need five Cacti to be sure that you don't let anything through which costs 125 sun more compared to just planting Peashooters there instead (for the same firepower but no anti-air capabilities). A Blover, on the other hand, costs 100 sun. So if you only see one wave of Balloon Zombies, the Blover becomes more cost efficient too! Besides, sometimes you just can't afford the extra time it takes to kill one more zombie, so you're really happy that you can instantly kill them with a Blover instead of just grounding them.
 * Averted in Blitzkrieg; if there are none of those pesky Messershimtz around, the AA guns will be just as happy to blast themselves some panzers instead.
 * Project Reality has anti-aircraft guns on many of the maps, and even has a class just for this role, toting a shoulder-launched SAM (Surface to Air Missile) such as the American-made FIM-92 Stinger or the Russian-made SA-7 Grail.
 * Many fighting games have attacks that are best used against those that like to "jump in," such as Ken and Ryu's Shoryuken and Guile's Flash Kick from Street Fighter, the standard uppercut from Mortal Kombat, and a good number of others.
 * Halo has the Anti Air Wraith. However, it only fires the slow-moving fuel rod gun bolts, which generally are useless against the types of aircraft used in the universe, As the wiki itself states, most deaths due to AA Wraiths are due to the pilot's stupidity.
 * Pokémon Black and White: the move Gravity nullifies Flying type's immunity to Ground attacks. There's also the Iron Ball item that also has the same effects when held. The move Roost is a self Anti Air move that nullifies the user's Flying type. Stealth Rock does extra damage to Flying-type Pokémon, among other types. Twister, Sky Uppercut, Gust, and Thunder do double damage to a Pokémon that's taken to the air. In addition, a new move called Smack Down involves throwing a rock at the opponent, which knocks flyers to the ground. It's funny having all your Pokemon use it at once in a 3-on-3 battle.
 * Anti-air techniques are so strong in Pokémon that Flying-types are rarely seen in competitive play, although the ability Levitate is seen frequently as it's not subject to the same anti-air rules as the Flying type.
 * Advance Wars' Anti-Air units (creatively called Anti-Airs) are essentially rapid-fire heavy machine guns on tracks. Not only are they devastating against air units, but against infantry and light vehicles as well. Against tanks however they are rubbish.

The Missile Launcher, meanwhile, is anti-air artillery capable of attacking aircraft up to five squares away. Being a SAM launcher it cannot attack non-aircraft at all.
 * Fire Emblem: bows are effective against winged enemies such as Pegasus and Wyvern units, and even Draco Zombies in The Sacred Stones.
 * Final Fantasy series
 * Aero spells, which are quite effective against flying enemies.
 * Wakka from Final Fantasy X specializes in striking airborne enemies as his basic physical attack. Other characters suffer a drop in accuracy against flying foes.
 * Final Fantasy XII; any large flying creatures can only be hit by using a projectile weapon, ie. bow, gun, or certain Techniks, like Telekinesis.
 * In Final Fantasy Crystal Chronicles, the Gravity spell grounds flying enemies so the player can attack them. Without it, flying enemies rarely suffer anything more than Scratch Damage from player attacks.
 * Some enemies have a skill called "100 G", which removes the Float status from all characters. (Fridge Logic: Shouldn't they be, like, Squashed Flat?)
 * Battlefield 2 features surface to air missile turrets on some maps as well as mobile anti-aircraft vehicles such as the American M6 Linebacker and the Russian 2S6M Tunguska. The USS Essex amphibious assault ship on some maps is also equipped with a Phalanx CIWS and Sea Sparrow missile system that can be operated by the player.
 * Starcraft - The Terran Missile Turret and Zerg Spore Colony are exclusively anti-air structures; the Zerg also have an anti-air suicide unit. The expansion Brood War gave each race a new flying anti-air only unit: Terrans got the Valkyrie, a ship with a splash-damage attack, Protoss got the Corsair, which relies on Beam Spam, and the Zerg got the Devourer, which uses a corrosive attack that slows attack and movement speed and reduces armor, which splashes and can be stacked.
 * Starcraft II also gives each race a flying AA unit: the Terrans get Vikings, which can switch between being anti-air-only fliers or anti-ground-only ground units at will. The Protoss get Phoenixes, which are essentially upgraded Corsairs with the ability to suspend ground units in the air temporarily, allowing other AA units to attack them. Finally, the Zerg get Corruptors, similar to Devourers except that their ability only increases the enemy's damage taken, is used separately rather than as an effect added to the basic attack, and doesn't splash or stack.

The Thor also has a devastating ground-to-air missile barrage attack, designed almost exclusively to take out groups of mutalisks.
 * Warcraft III: All races have some form of specialized air defense:
 * Humans have Aerial Shackles, which prevent the captured unit from moving or attacking while doing large amounts of damage all the while and can upgrade their Steam Tanks to fire rockets at multiple flyers simultaneously, and can also give their Flying Machines the ability to do splash damage to air units.
 * Undead' Crypt Fiends can shoot webs that force flyers to the ground so ground units can attack them, and have a strong anti-air Gargoyle.
 * Orcs can use nets to the same effect or use their Batriders' suicide attacks to deal large amounts of damage to multiple air units.
 * Night Elves can have their Hippogryph Riders dismount, turning a ranged air unit into a strong melee flyer and a ranged ground attacker in no time at all. Their entire army being based on multiple ranged units, flyers tend not to last very long against a volley of arrows.
 * Most ordinary combat units in Shattered Galaxy will usually have attacks dedicated to anti-air or anti-ground. There exist "versatile" units and weapons that can attack both, but they are generally considered to be unfit for either role, and therefore only good for beginners who have yet to learn the system.
 * World in Conflict has something in each role that can deal with targets in the air. Standard infantry squads carry a portable AA launcher, Support role has access to the best anti-air vehicles, and the Air role itself has helicopters with air-to-air missiles. True to the game's Rock-Paper-Scissors balance, the Ground role is the odd one out, with only one real AA-capable unit... and it'll still lose in a fair fight.
 * Command & Conquer usually follows the principle of having units and defense structures dedicated to either anti-ground or anti-air. That said:
 * This most frequently manifests as a Surface-to-Air Missile attack. Both sides in original C&C and Tiberian Sun have some kind of SAM structure.
 * The Red Alert 2 Soviets love their Flak cannons.
 * Allied AEGIS crusers in Red Alert 2 unleash a missile spam on air units, and only them. By comparison, GLA quad guns in Generals are as efficient on aircrafts as on infantry. As do the Chinese Gatling tank, which can actually shred infantry divisions with only a handful of them.
 * In Renegade, it is well possible to use a tank to fire at air units when you manage to target well enough.
 * In Command & Conquer: Red Alert 3, the trend is subverted with the Allies and the Imperials, since the Allies use the Multigunner system and the Imperials use the VX system; both let the commander choose what the turret's going to attack by putting infantry in and out of the turret or changing the configuration of the turret, respectively.
 * It's also subverted by most units in the game, since the two-weapon system allows some units a choice between anti-air and anti-ground, for example, the Chopper-VX, which is normally an anti-ground chopper but can be switched to an anti-air walker at will.
 * Tiberian Twilight nearly completely subverts the trope - because there's an entire Crawler class dedicated to air, most units now have the capability to strike air - the only exception, Cannon units.
 * Impossible Creatures has anti-air towers that unleash bolts of electricity on flying creatures. Given that flyers tend to have fairly low Hit Points and defense stats in the first place, they fall pretty quickly; however, these towers can't hurt land or water based units.
 * City of Heroes has many abilities that disable flight. A bit too many. Did you know getting hit with a slab of rock will prevent you from flying 20 seconds after impact? These were mostly added to balance PvP, but no one takes flight in PvP anyway because there are too many counters.
 * The Naval Ops games require you to mount anti-air weapons on your ships if you don't want to be blown to bits by swarms of enemy aircraft. SAMs can only target aircraft, but machine guns double as point defense weapons for taking down missiles and torpedos.
 * Operation Flashpoint appropriately features classic Real Life self-propelled AA artillery vehicles of its Cold War era setting : The ZSU-23-4 "Shilka" on the Soviet side and the M163 VADS "Vulcan" on the NATO side.
 * Joint Task Force has the SA-11 Russian SAM launcher. It can devastate flying targets at extreme ranges, but nothing else. You also have to capture it since it is not a NATO unit. On your side, you have the German Gepard Flakpanzer, which uses it´s two 35mm autocannons to great effect against light vehicles, light armor, helicopters, CAS-planes and, of course, Infantry. Tanks and other vehicles can use their mounted Heavy Machine Guns against helicopters for minimal damage, and Helicopters themselves can use their cannons against other helicopters.
 * In Gadget Trial, the Anti-Aircraft Artillery unit is the only surface (non-air) unit that can engage air units. It's usually a one hit kill, but it's also slow, poorly armored, and incapable of hitting anything else, and air units can take advantage of terrain defense bonuses, so for air defense, the player is advised to stick to fighters.
 * Flak towers and flak ships in Deadlock function as anti-air. Notably, everything else can attack aerial units, but only flak defense shuts them down entirely.
 * Just Cause 2 gives Rico access to Panuan military hardware, including anti-air flak guns which are hilariously useful against just about anything that happens to cross in front of them—infantry, helicopters, destroyable targets, all are handily shredded by the quad-barrel monstrosity.
 * Ground Control had missle-based AA terradynes for Crayven Corp and bullet-based AA hoverdynes for the Order of the New Dawn.
 * Similar to the Just Cause example above, the Order hoverdynes could hit buildings and ground units if they were on its line of fire even though they were not permitted to directly target these types of targets. Shredding is an accurate description to what happened to those buildings and (rarely) ground units hit by AA fire.
 * Actually the other way around. Dedicated Crayven AA terradynes fired a mass of projectiles while OND AA hoverdynes fired homing balls of lightning. Additionally, both sides had a support vehicle (missile terradyne and beam platform hoverdyne) that, while not quite as effective as the dedicated AA units, would make short work of enemy aerodynes and still could engage most ground targets.
 * Total Annihilation had missile units that could hit everything. They did pitiful damage, but they were only units that could track air units, which in turn had very low health. They ended up being spammed against ground targets anyway. The expansion pack added dedicated flak units that could only target aircraft, but destroyed them even more effectively.
 * Star Wars Galactic Battlegrounds has extremely fragile AA Troopers, less fragile AA Mobiles, decently durable AA turrets, and psychotically resilient Fortresses for all your AA needs. (Fortresses can shoot pretty much anything, since they're also fitted with ground-based lasers.) The general rule of thumb is that if it shoots rockets, it kills flyers.
 * Heavy Weapon has the Homing Missiles, which only target aerial enemies and actually do quite a good amount of damage to them. Best used against weak flying Mooks that come with more dangerous land troops (e.g. fighter jets along with tanks).
 * All ranged units in Rise of Legends can attack aircraft, but the Alin's Eternal Flame structure constantly spits bolts of fire at aircraft, and the Alin's Heartseeker unit is especially effective against air units. The Vinci and Cuotl prefer to use their own fighters to counter other air units, especially the Cuotl's Storm Disk.
 * Supreme Commander has two levels of ground-based mobile anti-air units. With the exception of the Cybran T1 anti-air gun, none of these units can target anything on the ground. On the other hand, all those guns on naval units aren't just for show; most ships have at least some kind of AA defenses in addition to their big guns: autoguns, flak cannons, SAMs/nanodart launchers, etc. Cruisers have serious anti-air capabilities in addition to their surface-to-surface cruise missiles. And we haven't even got to the kind of AA firepower some experimentals carry...

Real Life

 * In Real Life, the bulk of anti-aircraft weapons are specially designed for the role. Weapons designed to attack ground targets are often much less effective. For example, the sights on most firearms are not meant for firing into zenith—ballistics is tricky science. Throw in the fact that airplanes are rapidly moving targets, and it is obvious that the weapon will need a fancy targeting system, high muzzle velocity and a special mount to fire at steep angles. As a result, anti-air weapons are specialized and expensive. As such, it makes sense to use them in their intended capacity first and in all other capacities only as a last ditch effort.

That said, during WWII, AA guns were successfully repurposed. That high muzzle velocity was discovered to be just the thing against tanks—good for targeting, good for punching through. During the WW 2 many anti-air guns were put to anti-tank duty. Some even wound up being mounted on tanks and tank destroyers. The German 8.8 cm gun is the most famous example. Light, automatic, often multi-barreled anti-aircraft guns also proved to be brutal when used against infantry.

Additionally, while an individual rifleman poses little threat to aircraft, large numbers of infantry can damage low flying aircraft. For instance, at least three Argentinean jets were shot down in the Falklands by concerted small-arms fire alone. Furthermore, even minor damage can require hours of maintenance and checks to ensure the plane is airworthy. The Soviets were noted to take this to extremes during WWII, with everything from submachine guns to light mortars being fired in the direction of attacking aircraft.

Once miniaturized radar systems were developed, it was possible to put proximity fuses in pretty much any cannon shell turning any fast-traversing high-angled, long-barrel, high velocity cannon into a potential AA device. The US and UK deployed many cruisers with 5.25" and 6" dual purpose guns, every bit at home with shooting down bombers and blowing up enemy warships.

Large caliber guns are still used by the UK today for an AA role. The 4.5 inch Mk 8 Mod. 1 gun fitted to the majority of their frigates and destroyers is able to operate in a proximity fused mode, along with predictive radar aiming in order to act as a rather mean flak cannon. Especially when you consider that it is an auto loading cannon, capable of firing a shell every two seconds.
 * Not just in UK: the French firm GIAT builds a 100mm anti-air naval gun useful also for anti-ship combat and ground shelling used by various navies, and the Italian consortium Otobreda manufactures and sells the 127mm Compatto multipurpose gun (soon to be replaced with the similar but lighter 127 LW) and a 76mm gun whose two versions (Compatto, being more compact than the weapon it replaced, and the newer Super Rapid) are in use by 53 navies.
 * While fixed wing aircraft are usually fairly safe from anything not specifically designed to attack aircraft, it should be noted that helicopters are not quite so fortunate. Being much lower and slower flying, they're under threat not only from dedicated anti air platforms, but also from other weapons systems. General purpose guided missiles can typically still target them, being designed not only with anti tank work but also with versatility in mind. The same goes for cannons and unguided rockets designed to take down tanks, though some luck is required with the targeting. If the helicopter flies close enough to them, even infantry armed with machine guns can pose a threat by scoring a lucky hit on a weak spot like the tail rotor.
 * Not to mention that many helicopters are designed to transport troops, dropping them off and picking them up directly on the battlefield, meaning that they often have to hover in close proximity to their enemies, if not outright land on a battlefield. There is a well-founded saying about how all aircraft become targets once they are on the ground.