A-10 Warthog

The Fairchild Republic A-10 Thunderbolt II is an American twin-engine, straight wing jet aircraft developed by Fairchild-Republic in the early 1970s. It entered service in 1976, and is the only United States Air Force production-built aircraft designed solely for close air support, including attacking tanks, armored vehicles, and other ground targets. The A-10 was designed around the 30 mm GAU-8 Avenger rotary cannon that is its primary armament. The A-10's airframe was designed for durability, with measures such as 1,200 pounds (540 kg) of titanium armor to protect the cockpit and aircraft systems, enabling it to absorb a significant amount of damage and continue flying. Its short takeoff and landing capability permits operation from airstrips close to the front lines, while its simple design enables maintenance at forward bases with limited facilities.[4] The A-10A single-seat variant was the only version built, though one A-10A was converted to an A-10B twin-seat version. In 2005, a program was begun to upgrade remaining A-10A aircraft to the A-10C configuration. The A-10's official name comes from the Republic P-47 Thunderbolt of World War II, a fighter that was particularly effective at close air support. The A-10 is more commonly known by its nicknames "Warthog" or "Hog". Its secondary mission is to provide forward air controller - airborne (FAC-A) support, by directing other aircraft in attacks on ground targets. Aircraft used primarily in this role are designated OA-10. With a variety of upgrades and wing replacements, the A-10's service life may be extended to 2028.

Background
Criticism that the U.S. Air Force did not take close air support (CAS) seriously prompted a few service members to seek a specialized attack aircraft.[5][6] In the Vietnam War, large numbers of ground-attack aircraft were shot down by small arms, surface-to-air missiles, and low-level anti-aircraft gunfire, prompting the development of an aircraft better able to survive such weapons. In addition, the UH-1 Iroquois and AH-1 Cobra helicopters of the day, which USAF commanders had said should handle close air support, were ill-suited for use against armor, carrying only anti-personnel machine guns and unguided rockets meant for soft targets. Fast jets such as the F-100 Super Sabre, F-105 Thunderchief and F-4 Phantom II proved for the most part to be ineffective for close air support because their high speed did not allow pilots enough time to get an accurate fix on ground targets and they lacked sufficient loiter time. The effective, but aging, Korean War era A-1 Skyraider was the USAF's primary close air support aircraft.[7][8]

A-X program
In 1966, the USAF formed the Attack Experimental (A-X) program office.[9] On 6 March 1967, the Air Force released a request for information to 21 defense contractors for the A-X. The objective was to create a design study for a low-cost attack aircraft.[6] In 1969, the Secretary of the Air Force asked Pierre Sprey to write the detailed specifications for the proposed A-X project; Sprey's initial involvement was kept secret due to his earlier controversial involvement in the F-X project.[6] Sprey's discussions with Skyraider pilots operating in Vietnam and analysis of aircraft used in the role indicated the ideal aircraft should have long loiter time, low-speed maneuverability, massive cannon firepower, and extreme survivability;[6] possessing the best elements of the Ilyushin Il-2, Henschel Hs 129, and Skyraider. The specifications also demanded that each aircraft cost less than $3 million.[6] Sprey required that the biography of World War II Luftwaffe attack pilot Hans-Ulrich Rudel be read by people on the A-X program.[10] In May 1970, the USAF issued a modified, more detailed request for proposals (RFP) for the aircraft. The threat of Soviet armored forces and all-weather attack operations had become more serious. The requirements now included that the aircraft would be designed specifically for the 30 mm rotary cannon. The RFP also specified a maximum speed of 460 mph (400 kn; 740 km/h), takeoff distance of 4,000 feet (1,200 m), external load of 16,000 pounds (7,300 kg), 285-mile (460 km) mission radius, and a unit cost of US$1.4 million.[11] The A-X would be the first USAF aircraft designed exclusively for close air support.[12] During this time, a separate RFP was released for A-X's 30 mm cannon with requirements for a high rate of fire (4,000 round/minute) and a high muzzle velocity.[13] Six companies submitted aircraft proposals, with Northrop and Fairchild Republic selected to build prototypes: the YA-9A and YA-10A, respectively. General Electric and Philco-Ford were selected to build and test GAU-8 cannon prototypes.[14] Two YA-10 prototypes were built in the Republic factory in Farmingdale, New York and first flew on 10 May 1972 by pilot Howard "Sam" Nelson. Production A-10's were built at Fairchild in Hagerstown, Maryland. After trials and a fly-off against the YA-9, on 18 January 1973, the USAF announced the YA-10's selection for production.[15] General Electric was selected to build the GAU-8 cannon in June 1973.[16] The YA-10 had an additional fly-off in 1974 against the Ling-Temco-Vought A-7D Corsair II, the principal USAF attack aircraft at the time, in order to prove the need for a new attack aircraft. The first production A-10 flew in October 1975, and deliveries commenced in March 1976. In total, 715 airplanes were produced, the last delivered in 1984.[17]

One experimental two-seat A-10 Night Adverse Weather (N/AW) version was built by converting an A-10A.[18] The N/AW was developed by Fairchild from the first Demonstration Testing and Evaluation (DT&E) A-10 for consideration by the USAF. It included a second seat for a weapons system officer responsible for electronic countermeasures (ECM), navigation and target acquisition. The N/AW version did not interest the USAF or export customers. The two-seat trainer version was ordered by the Air Force in 1981, but funding was canceled by U.S. Congress and the jet was not produced.[19] The only two-seat A-10 built now resides at Edwards Air Force Base's Flight Test Center Museum.[20]

Upgrades
The A-10 has received many upgrades over the years. From 1978 onwards, the Pave Penny laser receiver pod was adopted, which receives reflected laser radiation from laser designators for faster and more accurate target identification.[21][22] The A-10 began receiving an inertial navigation system in 1980.[23] The Low-Altitude Safety and Targeting Enhancement (LASTE) upgrade provided computerized weapon-aiming equipment, an autopilot, and a ground-collision warning system. The A-10 is compatible with night vision goggles for low-light operation. In 1999, aircraft began receiving Global Positioning System navigation systems and a multi-function display.[24] The LASTE system was upgraded with Integrated Flight & Fire Control Computers (IFFCC).[25] An A-10A of pre-glass cockpit design

In 2005, the entire A-10 fleet began receiving the Precision Engagement upgrades that include an improved fire control system (FCS), electronic countermeasures (ECM), and smart bomb targeting. Aircraft which received this upgrade are redesignated A-10C; work was to be completed in 2011.[26] The Government Accounting Office in 2007 estimated the cost of upgrading, refurbishing, and service life extension plans for the A-10 force to total $2.25 billion through 2013.[12][27] The Air Force Material Command's Ogden Air Logistics Center at Hill AFB, Utah completed work on its 100th A-10 precision engagement upgrade in January 2008.[28] In 2007, the A-10 was subject to a service life extension program (SLEP);[29] Boeing was awarded a contract to build as many as 242 A-10 wing sets in June 2007.[30] In November 2011, two A-10s flew with the new wings fitted. In September 2013, the USAF awarded Boeing a $212 million follow-on contract for 56 new wings, increasing the total ordered to 173. Re-winging improves mission readiness, decreases maintenance costs, and allows the A-10 to be operated up to 2035.[31] In plans to retire the A-10, the USAF considered halting the wing replacement program, saving an additional $500 million on top of the total savings of retiring the fleet,[32] coming to $4.2 billion.[33] By May 2015, the re-winging program was too far into the contract to be financially efficient to cancel.[34]

In 2012, Air Combat Command requested the testing of a 600-gallon external fuel tank which would extend the A-10's loitering time by 45–60 minutes; flight testing of such a tank was conducted in 1997, but did not involve combat evaluation. Over 30 flight tests were conducted by the 40th Flight Test Squadron to gather data on the aircraft's handling characteristics and performance across different load configurations. The tank slightly reduced stability in the yaw axis, however there is no decrease in aircraft tracking performance.[35]

In July 2010, the USAF issued Raytheon a contract to integrate a Helmet Mounted Integrated Targeting (HMIT) system onto A-10Cs.[27] The Gentex Corporation Scorpion Helmet Mounted Cueing System (HMCS) was also evaluated.[36] In February 2014, Secretary of the Air Force Deborah Lee James ordered that development of Suite 8 software upgrade continue, in response to Congressional pressure. Software upgrades were originally to be ceased due to plans to retire the A-10. Suite 8 software includes IFF Mode 5, which modernizes the ability of friendly units to identify the A-10 as a friendly aircraft.[37]

Other uses
A-10 at RAF Fairford, 2005

On 25 March 2010, an A-10 conducted the first flight of an aircraft with all engines powered by a biofuel blend. The flight, performed at Eglin Air Force Base, used a 1:1 blend of JP-8 and Camelina-based fuel.[38] On 28 June 2012, the A-10 became the first aircraft to fly using a new fuel blend derived from alcohol; known as ATJ (Alcohol-to-Jet), the fuel is cellulousic-based that can be derived using wood, paper, grass, or any cellulose based material, and are fermented into alcohols before being hydro-processed into aviation fuel. ATJ is the third alternative fuel to be evaluated by the Air Force as a replacement for petroleum-derived JP-8 fuel. Previous types were a synthetic paraffinic kerosene derived from coal and natural gas and a bio-mass fuel derived from plant-oils and animal fats known as Hydroprocessed Renewable Jet.[39] In 2011, the National Science Foundation granted $11 million to modify an A-10 for weather research for CIRPAS at the U.S. Naval Postgraduate School,[40] replacing a retired North American T-28 Trojan.[41] The A-10's armor is expected to allow it to survive the extreme meteorological conditions, such as 200 mph hailstorms, found in inclement high-altitude weather events.[42] In 2015, Boeing revealed that it was holding initial discussions on the prospects of selling retired or stored A-10s in near-flyaway condition to international customers.[34] However, the Air Force subsequently stated that it will not permit the aircraft to be sold.[43]

Overview
A-10 inboard profile drawing

The A-10 has superior maneuverability at low speeds and altitude because of its large wing area, high wing aspect ratio, and large ailerons. The wing also allows short takeoffs and landings, permitting operations from primitive forward airfields near front lines. The aircraft can loiter for extended periods and operate under 1,000 ft (300 m) ceilings with 1.5 mi (2.4 km) visibility. It typically flies at a relatively low speed of 300 knots (350 mph; 560 km/h), which makes it a better platform for the ground-attack role than fast fighter-bombers, which often have difficulty targeting small, slow-moving targets.[7]

The leading edge of the wing has a honeycomb structure panel construction, providing strength with minimal weight; similar panels cover the flap shrouds, elevators, rudders and sections of the fins.[44] The skin panels are integral with the stringers and are fabricated using computer-controlled machining, reducing production time and cost. Combat experience has shown that this type of panel is more resistant to damage. The skin is not load-bearing, so damaged skin sections can be easily replaced in the field, with makeshift materials if necessary.[45] The ailerons are at the far ends of the wings for greater rolling moment and have two distinguishing features: The ailerons are larger than is typical, almost 50 percent of the wingspan, providing improved control even at slow speeds; the aileron is also split, making it a deceleron.[46][47]

The A-10 is designed to be refueled, rearmed, and serviced with minimal equipment.[48] Also, most repairs can be done in the field.[49] An unusual feature is that many of the aircraft's parts are interchangeable between the left and right sides, including the engines, main landing gear, and vertical stabilizers. The sturdy landing gear, low-pressure tires and large, straight wings allow operation from short rough strips even with a heavy aircraft ordnance load, allowing the aircraft to operate from damaged airbases, flying from taxiways or even straight roadway sections.[50]

Front view of an A-10 showing the 30 mm cannon and offset front landing gear

The front landing gear is offset to the aircraft's right to allow placement of the 30 mm cannon with its firing barrel along the centerline of the aircraft.[51] During ground taxi, the offset front landing gear causes the A-10 to have dissimilar turning radii. Turning to the right on the ground takes less distance than turning left.[Note 1] The wheels of the main landing gear partially protrude from their nacelles when retracted, making gear-up belly landings easier to control and less damaging. All landing gears are hinged toward the aircraft's rear; if hydraulic power is lost, a combination of gravity and wind resistance can open and lock the gear in place.[47]

Durability
The A-10 is exceptionally tough, being able to survive direct hits from armor-piercing and high-explosive projectiles up to 23 mm. It has double-redundant hydraulic flight systems, and a mechanical system as a back up if hydraulics are lost. Flight without hydraulic power uses the manual reversion control system; pitch and yaw control engages automatically, roll control is pilot-selected. In manual reversion mode, the A-10 is sufficiently controllable under favorable conditions to return to base, though control forces are greater than normal. The aircraft is designed to fly with one engine, one half of tail, one elevator, and half of a wing missing.[52]

The cockpit and parts of the flight-control system are protected by 1,200 lb (540 kg) of titanium aircraft armor, referred to as a "bathtub".[53][54] The armor has been tested to withstand strikes from 23 mm cannon fire and some strikes from 57 mm rounds.[49][53] It is made up of titanium plates with thicknesses from 0.5 to 1.5 inches (13 to 38 mm) determined by a study of likely trajectories and deflection angles. The armor makes up almost 6 percent of the aircraft's empty weight. Any interior surface of the tub directly exposed to the pilot is covered by a multi-layer nylon spall shield to protect against shell fragmentation.[55][56] The front windscreen and canopy are resistant to small arms fire.[57]

This A-10 suffered extensive damage during Operation Iraqi Freedom in 2003

The A-10's durability was shown on 7 April 2003 when Captain Kim Campbell, while flying over Baghdad during the 2003 invasion of Iraq, suffered extensive flak damage. Iraqi fire damaged an engine and crippled the hydraulic system, requiring the aircraft's stabilizer and flight controls to be operated via the 'manual reversion mode'. Despite this damage, Campbell flew the aircraft for nearly an hour and landed safely.[58][59]

The A-10 was envisioned to fly from forward air bases and semi-prepared runways with high risk of foreign object damage to the engines. The unusual location of the General Electric TF34-GE-100 turbofan engines decreases ingestion risk, and allows the engines to run while the aircraft is serviced and rearmed by ground crews, reducing turn-around time. The wings are also mounted closer to the ground, simplifying servicing and rearming operations. The heavy engines require strong supports, four bolts connect the engine pylons to the airframe.[60] The engines' high 6:1 bypass ratio have a relatively small infrared signature, and their position directs exhaust over the tailplanes further shielding it from detection by infrared homing surface-to-air missiles. The engines and their exhausts are angled upward by nine degrees to cancel out the nose-down pitching moment they would otherwise generate due to being mounted above the aircraft's center of gravity, avoiding the need to trim the control surfaces against the force.[60]

To reduce the likelihood of damage to the A-10's fuel system, all four fuel tanks are located near the aircraft's center and are separated from the fuselage; projectiles would need to penetrate the aircraft's skin before reaching a tank's outer skin.[55][56] Compromised fuel transfer lines self-seal; if damage exceeds a tank's self-sealing capabilities, check valves prevent fuel flowing into a compromised tank. Most fuel system components are inside the tanks so that fuel will not be lost due to component failure. The refueling system is also purged after use.[61] Reticulated polyurethane foam lines both the inner and outer sides of the fuel tanks, retaining debris and restricting fuel spillage in the event of damage. The engines are shielded from the rest of the airframe by firewalls and fire extinguishing equipment. In the event of all four main tanks being lost, two self-sealing sump tanks contain fuel for 230 miles (370 km) of flight.[55][56]

Weapons
A side-view drawing of the A-10's GAU-8/A Avenger gun and its approximate location in the fuselage

Although the A-10 can carry considerable disposable stores, its primary built-in weapon is the 30 mm GAU-8/A Avenger Gatling-type cannon. One of the most powerful aircraft cannon ever flown, it fires large depleted uranium armor-piercing shells. In the original design, the pilot could switch between two rates of fire: 2,100 or 4,200 rounds per minute;[62] this was changed to a fixed rate of 3,900 rounds per minute.[63] The cannon takes about half a second to come up to speed, so 50 rounds are fired during the first second, 65 or 70 rounds per second thereafter. The gun is accurate enough to place 80 percent of its shots within a 40-foot (12.4 m) diameter circle from 4,000 feet (1,220 m) while in flight.[64] The GAU-8 is optimized for a slant range of 4,000 feet (1,220 m) with the A-10 in a 30-degree dive.[65] Another view of the A-10's GAU-8 installation

The fuselage of the aircraft is built around the cannon. The GAU-8/A is mounted slightly to the port side; the barrel in the firing location is on the starboard side at the 9 o'clock position so it is aligned with the aircraft's centerline. The gun's 5-foot, 11.5-inch (1.816 m) ammunition drum can hold up to 1,350 rounds of 30 mm ammunition,[51] but generally holds 1,174 rounds.[65] To prevent enemy fire from causing the GAU-8/A rounds to fire prematurely, armor plates of differing thicknesses between the aircraft skin and the drum are designed to detonate incoming shells.[51][56] A final armor layer around the drum protects it from fragmentation damage. The gun is loaded by Syn-Tech's linked tube carrier GFU-7/E 30 mm ammunition loading assembly cart. The AGM-65 Maverick air-to-surface missile is a commonly used munition, targeted via electro-optical (TV-guided) or infrared. The Maverick allows target engagement at much greater ranges than the cannon, and thus less risk from anti-aircraft systems. During Desert Storm, in the absence of dedicated forward-looking infrared (FLIR) cameras for night vision, the Maverick's infrared camera was used for night missions as a "poor man's FLIR".[66] Other weapons include cluster bombs and Hydra rocket pods.[67] The A-10 is equipped to carry laser-guided bombs. A-10s usually fly with an ALQ-131 ECM pod under one wing and two AIM-9 Sidewinder air-to-air missiles under the other wing for self-defense.[68]

Modernization
A-10 Thunderbolt II, fully armed

The A-10 Precision Engagement Modification Program will update 356 A-10/OA-10s to the A-10C variant with a new flight computer, new glass cockpit displays and controls, two new 5.5-inch (140 mm) color displays with moving map function and an integrated digital stores management system.[12][27]

Other funded improvements to the A-10 fleet include a new data link, the ability to employ smart weapons such as the Joint Direct Attack Munition (JDAM) and Wind Corrected Munitions Dispenser, and the ability to carry an integrated targeting pod such as the Northrop Grumman LITENING or the Lockheed Martin Sniper Advanced Targeting Pod (ATP). Also included is the Remotely Operated Video Enhanced Receiver (ROVER) to provide sensor data to personnel on the ground.[26]

In 2016 the USAF announced a thick-skin urgent spares kitting (TUSK) wing assemblies program to extend the lifespan of the aircraft past 2040.[69]

Colors and markings
An A-10 from the 343rd Tactical Fighter Wing prepares to drop Mark 82 bombs at the Yukon Command Training Site in 1988.

Since the A-10 flies low to the ground and at subsonic speed, aircraft camouflage is important to make the aircraft more difficult to see. Many different types of paint schemes have been tried. These have included a "peanut scheme" of sand, yellow and field drab; black and white colors for winter operations and a tan, green and brown mixed pattern.[70] Many A-10s also featured a false canopy painted in dark gray on the underside of the aircraft, just behind the gun. This form of automimicry is an attempt to confuse the enemy as to aircraft attitude and maneuver direction.[71][72] Many A-10s feature nose art, such as shark mouth or warthog head features.

The two most common markings applied to the A-10 have been the European I woodland camouflage scheme and a two-tone gray scheme. The European woodland scheme was designed to minimize visibility from above, as the threat from hostile fighter aircraft was felt to outweigh that from ground-fire. It uses dark green, medium green and dark gray in order to blend in with the typical European forest terrain and was used from the 1980s to the early 1990s. Following the end of the Cold War, and based on experience during the 1991 Gulf War, the air-to-air threat was no longer seen to be as important as that from ground fire, and a new color scheme known as "Compass Ghost" was chosen to minimize visibility from below. This two-tone gray scheme has darker gray color on top, with the lighter gray on the underside of the aircraft, and started to be applied from the early 1990s.[73]

Introduction
Arkansas Air National Guard A-10C firing an AGM-65 air-to-surface missile on a firing range at Davis-Monthan AFB

The first unit to receive the A-10 Thunderbolt II was the 355th Tactical Training Wing, based at Davis-Monthan Air Force Base, Arizona, in March 1976. The first unit to achieve full combat-readiness was the 354th Tactical Fighter Wing at Myrtle Beach AFB, South Carolina, in 1978. Deployments of A-10As followed at bases both at home and abroad, including England AFB, Louisiana; Eielson AFB, Alaska; Osan Air Base, South Korea; and RAF Bentwaters/RAF Woodbridge, England. The 81st TFW of RAF Bentwaters/RAF Woodbridge operated rotating detachments of A-10s at four bases in Germany known as Forward Operating Locations (FOLs): Leipheim, Sembach Air Base, Nörvenich, and Ahlhorn.[74]

A-10s were initially an unwelcome addition to many in the Air Force. Most pilots switching to the A-10 did not want to because fighter pilots traditionally favored speed and appearance.[75] In 1987, many A-10s were shifted to the forward air control (FAC) role and redesignated OA-10.[76] In the FAC role the OA-10 is typically equipped with up to six pods of 2.75 inch (70 mm) Hydra rockets, usually with smoke or white phosphorus warheads used for target marking. OA-10s are physically unchanged and remain fully combat capable despite the redesignation.[77]

Gulf War and Balkans
A-10A after Operation Desert Storm, 1992

The A-10 was used in combat for the first time during the Gulf War in 1991, destroying more than 900 Iraqi tanks, 2,000 other military vehicles and 1,200 artillery pieces.[5] A-10s also shot down two Iraqi helicopters with the GAU-8 cannon. The first of these was shot down by Captain Robert Swain over Kuwait on 6 February 1991 for the A-10's first air-to-air victory.[78][79] Four A-10s were shot down during the war, all by surface-to-air missiles. Another three battle-damaged A-10s and OA-10As returned to base but were written off, some sustaining additional damage in crash landings.[80][81] The A-10 had a mission capable rate of 95.7 percent, flew 8,100 sorties, and launched 90 percent of the AGM-65 Maverick missiles fired in the conflict.[82] Shortly after the Gulf War, the Air Force abandoned the idea of replacing the A-10 with a close air support version of the F-16.[83]

An A-10A during Operation Allied Force

U.S. Air Force A-10 aircraft fired approximately 10,000 30 mm rounds in Bosnia and Herzegovina in 1994–95. Following the seizure of some heavy weapons by Bosnian Serbs from a warehouse in Ilidža, a series of sorties were launched to locate and destroy the captured equipment. On 5 August 1994, two A-10s located and strafed an anti-tank vehicle. Afterward, the Serbs agreed to return remaining heavy weapons.[84] In August 1995, NATO launched an offensive called Operation Deliberate Force. A-10s flew close air support missions, attacking Bosnian Serb artillery and positions. In late September, A-10s began flying patrols again.[85]

A-10s returned to the Balkan region as part of Operation Allied Force in Kosovo beginning in March 1999.[85] In March 1999, A-10s escorted and supported search and rescue helicopters in finding a downed F-117 pilot.[86] The A-10s were deployed to support search and rescue missions, but over time the Warthogs began to receive more ground attack missions. The A-10's first successful attack in Operation Allied Force happened on 6 April 1999; A-10s remained in action until combat ended in late June 1999.[87]

Afghanistan, Iraq, Libya, and recent deployments
A-10 over Afghanistan, 2011

During the 2001 invasion of Afghanistan, A-10s did not take part in the initial stages. For the campaign against Taliban and Al Qaeda, A-10 squadrons were deployed to Pakistan and Bagram Air Base, Afghanistan, beginning in March 2002. These A-10s participated in Operation Anaconda. Afterwards, A-10s remained in-country, fighting Taliban and Al Qaeda remnants.[88]

Operation Iraqi Freedom began on 20 March 2003. Sixty OA-10/A-10 aircraft took part in early combat there.[89] United States Air Forces Central Command issued Operation Iraqi Freedom: By the Numbers, a declassified report about the aerial campaign in the conflict on 30 April 2003. During that initial invasion of Iraq, A-10s had a mission capable rate of 85 percent in the war and fired 311,597 rounds of 30 mm ammunition. A single A-10 was shot down near Baghdad International Airport by Iraqi fire late in the campaign. The A-10 also flew 32 missions in which the aircraft dropped propaganda leaflets over Iraq.[90]

A-10s at Tallil Air Base, Iraq of the Air Force Reserve Command's 442nd Fighter Wing, in 2009

The A-10C first deployed to Iraq in 2007 with the 104th Fighter Squadron of the Maryland Air National Guard. The jets include the Precision Engagement Upgrade.[91] The A-10C's digital avionics and communications systems have greatly reduced the time to acquire a close air support target and attack it.[92]

A-10s flew 32 percent of combat sorties in Operation Iraqi Freedom and Operation Enduring Freedom. The sorties ranged from 27,800 to 34,500 annually between 2009 and 2012. In the first half of 2013, they flew 11,189 sorties in Afghanistan.[93] From the beginning of 2006 to October 2013, A-10s flew 19 percent of CAS operations in Iraq and Afghanistan, more than the F-15E Strike Eagle or B-1B Lancer, but less than the 33 percent of CAS missions flown by F-16s during that time period.[94]

An A-10 peels away from a KC-135 Stratotanker while flying over Afghanistan, February 2011

In March 2011, six A-10s were deployed as part of Operation Odyssey Dawn, the coalition intervention in Libya. They participated in attacks on Libyan ground forces there.[95][96]

In September 2014, the USAF 122nd Fighter Wing revealed it would be deploying to the Middle East in the next month, which includes 12 of the unit's 21 A-10 aircraft. Although the deployment had been planned a year in advance in a support role, the timing coincided with the ongoing Operation Inherent Resolve against Islamic State militants.[97][98][99] Since mid-November, U.S. commanders began sending A-10s to hit IS targets in central and northwestern Iraq on an almost daily basis.[100][101] In about two months time, A-10s flew 11 percent of all USAF sorties since the start of operations in August 2014.[102] On 15 November 2015, two days after the ISIL attacks in Paris, A-10s and AC-130s destroyed a convoy of over 100 ISIL-operated oil tanker trucks in Syria. The attacks were part of an intensification of the U.S.-led intervention against ISIL called Operation Tidal Wave II (named after the original Operation Tidal Wave during World War II, a failed attempt to raid German oil fields that resulted in heavy aircraft and aircrew loss) in an attempt to cut off oil smuggling as a source of funding for the group.[103]

Future
23rd Fighter Group A-10 Thunderbolt IIs on alert

In 2007, the A-10 was expected to be in USAF service until 2028 and possibly later,[104] when it may be replaced by the Lockheed Martin F-35 Lightning II.[29] Critics have said that replacing the A-10 with the F-35 would be a "giant leap backwards" given the A-10's performance and the F-35's rising costs.[105] In 2012, the Air Force considered the F-35B STOVL variant as a replacement CAS aircraft, but concluded that the aircraft could not generate sufficient sorties.[106] In August 2013, Congress and the Air Force examined various proposals, including the F-35 and the MQ-9 Reaper unmanned aerial vehicle filling the A-10's role. Proponents state that the A-10's armor and cannon are superior to aircraft such as the F-35 for ground attack, that guided munitions other planes rely upon could be jammed, and that ground commanders frequently request A-10 support.[93]

In the USAF's FY 2015 budget, the service considered retiring the A-10 and other single-mission aircraft, prioritizing multi-mission aircraft; cutting a whole fleet and its infrastructure was seen as the only method for major savings. The U.S. Army had expressed interest in obtaining some A-10s should the Air Force retire them,[107][108] but later stated there was "no chance" of that happening.[109] The U.S. Air Force stated that retirement would save $3.7 billion from 2015 to 2019. Guided munitions allow more aircraft to perform the CAS mission, reducing the requirement for a specialized aircraft; since 2001, multirole aircraft and bombers performed 80 percent of CAS missions. The Air Force stated the A-10 is also more vulnerable to advanced anti-aircraft defenses. The Army stated that the A-10 is invaluable for its versatile weapons loads, psychological impact, and reduced logistics needs on ground support systems.[110]

In January 2015, USAF officials told lawmakers that it would take 15 years to fully develop a new attack aircraft to replace the A-10;[111] service leaders admit a follow-on weapon system for the A-10 is "on the table."[112] It planned for F-16s and F-15Es to initially take up CAS sorties, and later by the F-35A once sufficient numbers become operationally available over the next decade. The service is considering purchasing a relatively inexpensive replacement to perform CAS against enemies that lack sophisticated air defenses.[113] As of 2015, the US Air Combat Command is considering developing a replacement aircraft.[114][115] In January 2016, the USAF revealed it was "indefinitely freezing" plans to retire the A-10 for at least several years. In addition to Congressional opposition, its use in anti-ISIL operations, deployments to Eastern Europe as a response to Russia's military intervention in Ukraine, and reevaluation of F-35 numbers necessitated its retention.[116][117] Retirement has been deferred until 2022 when F-35s will begin replacing it on a squadron-by-squadron basis.[118]

Variants
A newly updated A-10C arrives at Davis-Monthan AFB, 29 November 2006.
 * YA-10A
 * Pre-production variant. 12 were built.[119]


 * A-10A
 * Single-seat close air support, ground-attack version. (All updated to A-10C)


 * OA-10A
 * A-10As used for airborne forward air control. (All updated to A-10C)


 * YA-10B Night/Adverse Weather
 * Two-seat experimental prototype, for work at night and in bad weather. The one YA-10B prototype was converted from an A-10A.[120]


 * A-10C
 * A-10As updated under the incremental Precision Engagement (PE) program.[26]


 * A-10PCAS
 * Proposed unmanned version developed by Raytheon and Aurora Flight Sciences as part of DARPA's Persistent Close Air Support program.[121] The PCAS program eventually dropped the idea of using an optionally manned A-10.[122]


 * Civilian A-10
 * Proposed by the South Dakota School of Mines and Technology to replace its North American T-28 Trojan

thunderstorm penetration aircraft. The A-10 would have its military engines, avionics, and oxygen system replaced by civilian versions. The engines and airframe would receive protection from hail, and the GAU-8 Avenger would be replaced with ballast or scientific instruments.[123] ☀Role Fixed-wing close air support, forward air control, and ground-attack aircraft National origin United States Manufacturer Fairchild Republic First flight 10 May 1972 Introduction March 1977 Status In service Primary user United States Air Force Produced 1972–84[1]

Number built 716[2]

Unit cost

US$18.8 million[3]