The Air Defense has an excellent range and a very high damage per shot. As the in-game description states, it's best to position them so that they cover as much area as possible. One common strategy for Town Hall 7 and above is to position them in a wide triangle (or diamond, once the fourth Air Defense is available) around the Town Hall.
If possible, keep your Air Defenses behind your first lines of defense (e.g. Cannons and Archer Towers), preferably with a Wall in between. This will prevent a large Giant or Golem assault from quickly destroying the Air Defense and allowing a Healer to be deployed early in the battle. The longer it takes the Giants to destroy the Air Defense, the more time your turrets will have to thin out their ranks before a Healer can be safely deployed.
The Air Defense is a natural target to attack first, as clearing them helps pave the way for an air assault. Healers are very vulnerable to the Air Defense, destroying this defence with Giants before deploying her is recommended. They are easily destroyed by any ground-based troop, as they cannot fight back.
It is advisable to keep Balloons away from Air Defenses, as they are capable of destroying most Balloons in one or two hits from a great distance.
Although Air Defenses are quite effective against Dragons, it is possible to keep an Air Defense occupied with a one or two Dragons for a fleet of Balloons to quickly destroy a majority of the ground defenses.
A great way to overwhelm the Air Defense is using a large group of Minions since the Air Defense can only target one air unit at a time.
A good strategy placement for this defense is by placing it near a Wizard Tower (which would be near a Mortar and a storage, for maximum protection).
Air Defenses undergo significant visual changes at levels 2 through 8.
When initially constructed, the Air Defense consists of a single wooden launch tube with a single red-and-black rocket. The launch tube is banded with metal.
At levels 2 and 3, an additional launch tube with a rocket inside is added.
At level 4, the three wooden launch tubes merge into one and gain an additional rocket. The launch base is reinforced with metal.
At levels 5 and 6, another launch tube and rocket are added.
At level 7, the three launch tubes are replaced with a single large wooden launcher with four large black and yellow rockets in it.
At level 8, the Air Defense's launcher receives a coat of red paint, along with dark metal bands and golden rivets. It is filled with four large, black-tipped rockets that are painted in a yellow and black chessboard pattern, similar to that seen on the V-2 Rocket.
The rockets in the launcher look like fireworks. When they explode, you can see a small show of lights if you zoom in close enough.
The visual representation of rockets in the Air Defense's launchers does not represent the amount of ammunition the Air Defense contains. The Air Defense has unlimited ammunition and will continue to fire as long as the enemy has any surviving Air Troops in range.
In most English-speaking countries outside the United States, the Air Defense is called the Air Defence.
Oddly, even though at level 1 where it is mostly made of wood, the Air Defense possesses 800 hitpoints, which outnumbers that of the far sturdier-looking level 9 Archer Tower, with 750 hitpoints, and almost equal to the level 10 Archer Tower with 810 hitpoints, which looks just as sturdy as its precursor.
The Air Defense had a significant visual change for most levels in the 21/3 Bowler Update.
Tapping this icon displays information about the Air Defense, such as Level, Damage Per Second, Hitpoints, Range, Damage Type and Targets.
Tapping this icon begins upgrading the Air Defense to the next level, if you have enough resources and a free Builder. When the Air Defense is at maximum level, this icon is not shown.
Tapping this icon instantly upgrades the Air Defense to the next level, at the cost of one Hammer of Building if you have one. When the Air Defense is at maximum level, this icon is not shown.
Tapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of the displayed number of Gems.
Tapping this icon, which is displayed only while an upgrade is in progress, instantly finishes that upgrade at the cost of one Book of Building. This icon is only shown if you have at least one Book of Building.
Tapping this icon, which is displayed only while an upgrade is in progress, boosts all your Builders for 1 hour by a factor of ten, at the cost of one Builder Potion. This icon is only shown if you have at least one Builder Potion.
Tapping this icon, which is displayed only while an upgrade is in progress, cancels the current upgrade and refunds half of the upgrade cost.