The AV-8B underwent standard evaluations to prepare for its USMC service. In the operational evaluation (OPEVAL), lasting from 31 August 1984 to 30 March 1985, four pilots and a group of maintenance and support personnel tested the aircraft under combat conditions. The aircraft was graded for its ability to meet its mission requirements for navigating, acquiring targets, delivering weapons, and evading and surviving enemy actions, all at the specified range and payload limits. The first phase of OPEVAL, running until 1 February 1985, required the AV-8B to fly both deep and close air support missions (deep air support missions do not require coordination with friendly ground forces) in concert with other close-support aircraft, as well as flying battlefield interdiction and armed reconnaissance missions. The aircraft flew from military installations at Marine Corps Base Camp Pendleton and Naval Air Weapons Station China Lake in California, Canadian Forces Base Cold Lake in Canada, and MCAS Yuma in Arizona.
The second phase of OPEVAL, which took place at MCAS Yuma from 25 February to 8 March, required the AV-8B to perform fighter escort, combat air patrol, and deck-launched intercept missions. Although the evaluation identified shortfalls in the design (subsequently rectified), OPEVAL was deemed successful. The AV-8B Harrier II reached initial operating capability (IOC) in January 1985 with USMC squadron VMA-331.
Front-view of gray jet aircraft executing a hover. The huge engine inlets are on both sides of the fuselage
An AV-8B hovering during the 2012 Miramar Air Show
The AV-8B saw extensive action in the Gulf War of 1990–91. Aircraft based on USS Nassau and Tarawa, and at on-shore bases, initially flew training and support sorties, as well as practicing with coalition forces. The AV-8Bs were to be held in reserve during the initial phase of the preparatory air assault of Operation Desert Storm. The AV-8B was first used in the war on the morning of 17 January 1991, when a call for air support from an OV-10 Bronco forward air controller against Iraqi artillery that was shelling Khafji and an adjacent oil refinery, brought the AV-8B into combat. The following day, USMC AV-8Bs attacked Iraqi positions in southern Kuwait. Throughout the war, AV-8Bs performed armed reconnaissance and worked in concert with coalition forces to destroy targets.
During Operations Desert Shield and Desert Storm, 86 AV-8Bs amassed 3,380 flights and about 4,100 flight hours, with a mission availability rate of over 90 percent. Five AV-8Bs were lost to enemy surface-to-air missiles, and two USMC pilots were killed. The AV-8B had an attrition rate of 1.5 aircraft for every 1,000 sorties flown. US Army General Norman Schwarzkopf later named the AV-8B among the seven weapons—along with the F-117 Nighthawk and AH-64 Apache—that played a crucial role during the war. In the aftermath of the war, from 27 August 1992, until 2003, USMC AV-8Bs and other aircraft patrolled Iraqi skies in support of Operation Southern Watch. The AV-8Bs launched from amphibious assault ships in the Persian Gulf, and from forward operating bases such as Ali Al Salem Air Base, Kuwait.
In 1999, the AV-8B participated in NATO's bombing of Yugoslavia during Operation Allied Force. Twelve Harriers were split evenly between the 24th and 26th Marine Expeditionary Units (MEU). AV-8Bs of the 24th MEU were introduced into combat on 14 April, and over the next 14 days flew 34 combat air support missions over Kosovo. During their six-month deployment aboard USS Nassau, 24th MEU Harriers averaged a high mission-capable rate of 91.8 percent. On 28 April, the 24th MEU was relieved by the 26th MEU, based on USS Kearsarge. The first combat sorties of the unit's AV-8Bs occurred two days later, one aircraft being lost. The 26th MEU remained in the theater of operations until 28 May, when it was relocated to Brindisi, Italy.
USMC AV-8Bs took part in Operation Enduring Freedom in Afghanistan from 2001. The USMC 15th MEU arrived off the coast of Pakistan in October 2001. Operating from the unit's ships, four AV-8Bs began attack missions into Afghanistan on 3 November 2001. The 26th MEU and its AV-8Bs joined 15th MEU later that month. In December 2001, AV-8Bs began moving into Afghanistan to a forward base at Kandahar. More AV-8Bs were deployed with other USMC units to the region in 2002. The VMA-513 squadron deployed six Night Attack AV-8Bs to Bagram in October 2002. These aircraft each carried a LITENING targeting pod to perform reconnaissance missions along with attack and other missions, primarily at night.
A jet aircraft hovering above flight deck of a large military ship, with several aircraft visible on the deck.
A USMC AV-8B hovers as many more are parked on the deck of amphibious assault ship USS Bataan, one month after the start of Operation Iraqi Freedom
The aircraft participated in Operation Iraqi Freedom in 2003, acting primarily in support of USMC ground units. During the initial action, 60 AV-8Bs were deployed on ships such as the USS Bonhomme Richard and Bataan, from which over 1,000 sorties were flown throughout the war. When possible, land-based forward arming and refuelling points were set up to enable prompt operations. USMC commander Lieutenant General Earl B. Hailston said that the Harriers were able to provide 24-hour support for ground forces, and noted that "The airplane ... became the envy of pilots even from my background ... there's an awful lot of things on the Harrier that I've found the Hornet pilots asking me [for] ... We couldn't have asked for a better record".
USMC sources documented the Harrier as holding an 85 percent aircraft availability record in the Iraq War; in just under a month of combat, the aircraft flew over 2,000 sorties. When used, the LITENING II targeting pod achieved greater than 75 percent kill effectiveness on targets. In a single sortie from USS Bonhomme Richard, a wave of Harriers inflicted heavy damage on a Republican Guard tank battalion in advance of a major ground assault on Al Kut. Harriers regularly operated in close support roles for friendly tanks, one of the aircraft generally carrying a LITENING pod. Despite the Harrier's high marks, the limited amount of time that each aircraft could remain on station, around 15–20 minutes, led to some calls from within the USMC for the procurement of AC-130 gunships, which could loiter for six hours and had a heavier close air support capability than the AV-8B. AV-8Bs were later used in combination with artillery to provide constant fire support for ground forces during heavy fighting in 2004 around the insurgent stronghold of Fallujah. The urban environment there required extreme precision for airstrikes.
On 20 March 2011, USMC AV-8Bs were launched from USS Kearsarge in support of Operation Odyssey Dawn, enforcing the UN no-fly zone over Libya. They carried out airstrikes on Sirte on 5 April 2011. Multiple AV-8Bs were involved in the defense of a downed F-15E pilot, attacking approaching Libyans prior to the pilot's extraction by a MV-22 Osprey.
In addition to major conflicts, USMC AV-8Bs have been deployed in support of contingency and humanitarian operations, providing fixed-wing air cover and armed reconnaissance. The aircraft served in Somalia throughout the 1990s, Liberia (1990, 1996, and 2003), Rwanda (1994), Central African Republic (1996), Albania (1997), Zaire (1997), and Sierra Leone (1997).
During its service with the USMC, the Harrier has had an accident rate three times that of the Corps' F/A-18s. The AV-8 was dubbed a "widow maker" by some in the military. The Los Angeles Times reported in 2003 that the Harrier family had the highest rate of major accidents among military aircraft in service then, with 148 accidents and 45 people killed. Lon Nordeen notes that several other USMC single-engine strike aircraft, like the A-4 Skyhawk and A-7 Corsair II, had worse accident rates. The Harrier's high accident rate is largely due to the higher percentage of time it spends taking off and landing, which are the most critical times in flight.
The AV-8B is to be replaced by the F-35B version of the Lockheed Martin F-35 Lightning II, which had been slated to enter service in 2012. The USMC had sought a replacement since the 1980s, and has argued strongly in favor of the development of the F-35B. The Harrier's performance in Iraq, including its ability to use forward operating bases, reinforced the need for a V/STOL aircraft in the USMC arsenal. In November 2011, the USN purchased the UK's fleet of 72 retired BAe Harrier IIs (63 single-seat GR.7/9/9As plus 9 twin-seat T.12/12As) and replacement engines to provide spares for the existing USMC Harrier II fleet. Although the March 2012 issue of the magazine AirForces Monthly stated that the USMC intended to fly some of the ex-British Harrier IIs, instead of using them just for spare parts, the Naval Air Systems Command (NAVAIR) has since stated that the USMC has never had any plans to operate those Harriers.
On 14 September 2012, a Taliban raid destroyed six AV-8Bs and severely damaged two others while they were parked on the tarmac at Camp Bastion in Afghanistan's Helmand Province. All of the aircraft belonged to VMA-211. The two damaged AV-8Bs were flown out of Afghanistan in the hours after the attack. The attack was described as "the worst loss of U.S. airpower in a single incident since the Vietnam War." The lost aircraft were quickly replaced by those from VMA-231.
On 27 July 2014, the USS Bataan began deploying USMC AV-8Bs over Iraq to provide surveillance of Islamic State (IS) forces. Surveillance operations continued after the start of Operation Inherent Resolve against IS militants. In early September 2014, a USMC Harrier from the 22nd MEU struck an IS target near the Haditha Dam in Iraq, marking the first time a USMC unit dropped ordnance in the operation.