AV-8B Harrier II

The Boeing AV-8B Harrier is a VTOL (Vertical Take Off and Landing) fighter jet used by the United States Marine Corps and the Royal Air Force/ Navy. It appears in Call of Duty 4: Modern Warfare and Call of Duty: Modern Warfare 2. The Harrier is used by the USMC to support their amphibious landing operations. They usually carry out airstrikes against enemy fortifications and units in support of friendlies. As a VTOL aircraft, it is capable of hovering in place like a helicopter, though it mostly relies on its speed to avoid enemy fire. It is slightly slower than most attack fighters, which is why it is more useful in a Ground Support role.

Call of Duty 4: Modern Warfare
A flight of USMC AV-8B jets appear in the mission Heat, callsign Falcon One. They provide close air support to the S.A.S. team using cluster bombs. Additionally the player can see Harriers bombing targets in the mission Shock and Awe ahead of the Marine assault, thereby reducing resistance to a ground assault by the Marines. Two of the jets fly right over the player's position in the mission Charlie Don't Surf when they are on the roof of the TV station.

Call of Duty: Modern Warfare 2
Campaign 

The Harrier also makes a handful of appearances in Campaign, though they are seen far less often than in Call of Duty 4, with the F-15 Eagle replacing them in the role of Close-Air Support. A pair of them can be seen showing off their VTOL capability in the level Exodus.

Multiplayer
The Harrier strike is an unlockable kill streak in Call of Duty: Modern Warfare 2. Requiring 7 consecutive kills, or 6 with the hardline perk. It deploys a smaller airstrike than the Precision Airstrike, but the third Harrier will stay hovering and guard a specific area, firing its machine guns at all enemies within that area. The Harrier does not stay completely fixed in place, and will move a little bit, but generally stays around the same area.

Trivia

 * In online play, if a player gets the final killcam with a Harrier, they will complete a challenge called "True Liar"- obviously a reference to the movie True Lies, in which the climax takes place on the aircraft.
 * In many ways, the Harrier Strike is completely inaccurate with how it works, let alone the design of the aircraft. The Harrier is not designed to hover around for long periods of time, only for take off and landing. The second inconsistency, is its gun; the Harrier does not possess an under mounted turret as seen on the one in-game; instead it is equipped with the GAU-12 "Equalizer" which is mounted in a detachable gunpod under the fuselage of the aircraft.
 * The Harrier being in US service in 2016 is inaccurate, as the F-35 Lightning II is scheduled to replace it in service in 2012.
 * If another enemy attack aircraft (An attack helicopter, for example) appears, the Harrier will attempt to fight it and will begin to fire missiles at it.
 * The Harrier Strike is a highly popular choice for a killstreak reward as unlike other AI air support, the kills gained by the airstrike and the harrier add to your killstreak. This makes the Harrier strike a very effective mid-streak reward used to work towards your highest reward, like the Chopper Gunner and The Nuke.
 * The Harrier is worth 300 exp points if shot down during a multi-player match