A U.S. Air Force A-10 Thunderbolt II flies overhead July 15, 2017, at Incirlik Air Base, Turkey. The A-10s are deployed here from the 74th Fighter Squadron, Moody Air Force Base, Georgia, in support of Operation Inherent Resolve. A U.S. Air Force A-10 Thunderbolt II taxis to a parking spot from the flight line July 15, 2017, at Incirlik Air Base, Turkey. The A-10s are deployed here from the 74th Fighter Squadron, Moody Air Force Base, Georgia, in support of Operation Inherent Resolve. (U.S. Air Force photo by Airman 1st Class Kristan Campbell) 4 of 4 DOWNLOAD HI-RES / PHOTO DETAILS A U.S. Air Force A-10 Thunderbolt II taxis to a parking spot from the flight line July 15, 2017, at Incirlik Air Base, Turkey. The A-10s are deployed here from the 74th Fighter Squadron, Moody Air Force Base, Georgia, in support of Operation Inherent Resolve. (U.S. Air Force photo by Airman 1st Class Kristan Campbell) An A-10 Thunderbolt II taxis on the runway July 15, 2017, at Incirlik Air Base, Tur (Kristan Campbell/U.S. Air Force)

A U.S. Air Force A-10 Thunderbolt II flies overhead July 15, 2017, at Incirlik Air Base, Turkey. The A-10s are deployed here from the 74th Fighter Squadron, Moody Air Force Base, Georgia, in support of Operation Inherent Resolve. A U.S. Air Force A-10 Thunderbolt II taxis to a parking spot from the flight line July 15, 2017, at Incirlik Air Base, Turkey. The A-10s are deployed here from the 74th Fighter Squadron, Moody Air Force Base, Georgia, in support of Operation Inherent Resolve. (U.S. Air Force photo by Airman 1st Class Kristan Campbell) 4 of 4 DOWNLOAD HI-RES / PHOTO DETAILS A U.S. Air Force A-10 Thunderbolt II taxis to a parking spot from the flight line July 15, 2017, at Incirlik Air Base, Turkey. The A-10s are deployed here from the 74th Fighter Squadron, Moody Air Force Base, Georgia, in support of Operation Inherent Resolve. (U.S. Air Force photo by Airman 1st Class Kristan Campbell) An A-10 Thunderbolt II taxis on the runway July 15, 2017, at Incirlik Air Base, Tur (Kristan Campbell/U.S. Air Force)

A pilot conducts a preflight check on an A-10 Thunderbolt II on July 11, 2017, at Incirlik Air Base, Turkey. The A-10s support ground forces with rapid employment close air and contact support. It utilizes a variety of bomb, missiles and a 30mm GAU-8 seven-barrel Gatling gun. (407th Air Expeditionary Group)

A maintainer from the 447th Expeditionary Aircraft Maintenance Squadron prepares an A-10 Thunderbolt II July 11, 2017, at Incirlik Air Base, Turkey. (Ramon Adelan/U.S. Air Force)

IRBIL, Iraq — Proving it’s not too old for new tricks, an aging A-10 attack plane dropped a bunker-busting bomb for the first time in combat earlier in August against an Islamic State target in Syria, defense officials said.

Despite efforts to put it out to pasture, the 1970s-era A-10 Thunderbolt II, known affectionately as the “Warthog,” has been a workhorse in the U.S.-led anti-Islamic State coalition since November 2014.

A dozen A-10s based at Incirlik Air Base in Turkey average 750 strikes a month against ISIS, according to an Air Force video that showed a combat-effective 2,000-pound, GPS-guided GBU-31 version 3 being loaded onto one of the airframes for the first time, alongside a general-purpose variant.

On Aug. 8, an A-10 dropped the bunker-buster on a building in the ISIS capital of Raqqa, where enemy snipers were targeting coalition troops and partnered Syrian Diplomatic Forces, a U.S. Air Force Central Command spokesman said.

“The weapon was selected for its ability to penetrate deeply into this particular structure,” Air Force Capt. Jose Davis said via email.

The 74th Fighter Squadron “Flying Tigers” deployed a dozen A-10s from Moody Air Force Base, Ga., to Turkey in July in support of the ISIS fight.

Regarded as “flying tanks,” the aircraft is beloved by ground forces for unmatched close air support capabilities, but the Air Force has said it can’t afford to maintain both the Warthogs and the multi-role F-35 meant to replace them. Lawmakers have fought to keep them flying into the next decade.

There are currently no A-10s supporting U.S. forces in Afghanistan in their dual missions of fighting terrorists and supporting Afghan forces, but defense officials are reportedly mulling a deployment of the aircraft under President Donald Trump’s new South Asia strategy, which would also add thousands of troops to the fight there.

Though the A-10’s first combat use of the bomb came this month, the bunker busters have already been used extensively against ISIS militants by other aircraft, Davis said — more than 7,500 have been dropped so far. Air Force F-15 and F-16 fighter jets and B-52 and B-1 bombers can also employ the bomb, which is accurate to within 10 feet “every day and in every condition.”

Senior Airman Joshua Coll, a weapons lead crew member who loaded the bombs, says in the Air Force video that he feels “absolute satisfaction” seeing the planes go out with bombs he loaded and return without them.

“That means that hostile targets died,” Coll said. “That means that we got the mission done.”

Coalition air support has proven critical in fighting ISIS, especially in its urban strongholds, where the group is dug in for a fight against U.S.-backed Iraqi and Syrian forces. That airpower is now heavily focused on helping Syrian Democratic Forces retake Raqqa, the capital of ISIS’s self-proclaimed caliphate and the coalition’s top priority now, where fighting is in its third month.

ISIS’s defenses have included underground tunnel systems and networks of passageways linking whole blocks of concrete houses, concealing fighter’s movements and protecting deadly arsenals. Snipers hidden inside multi-story concrete buildings have wrought havoc on civilians as well as com-batants.

But the jihadis lack any serious anti-aircraft capability, allowing coalition aircraft to loiter unmolested for long periods over their targets. The militants have used heavy machine guns on occasion to try and engage the circling warplanes and drones, but these have generally kept well above the automatic weapons’ maximum range. ISIS did manage to shoot down a low-flying Russian Mi-25 gunship in Syria last year, but this was accomplished using an anti-tank missile — a hit not likely to be repeated soon.

The GBU-31 version 3 helps the coalition take out “exceptionally difficult targets like bunkers or deeply buried or hardened facilities ISIS may use in support of its war machine,” while minimizing unintended collateral damage, Davis said.

It pairs a joint direct attack munitions, or JDAM, guidance kit with a bomb body that has a one-inch-thick casing made of a single, high-strength piece of forged steel and can penetrate up to six feet of reinforced concrete, according to an Air Force fact sheet. A delayed-action fuse then detonates 550 pounds of high-explosive Tritonal.

The version 3 is “a less explosive weapon and more of a penetrating munition,” Davis said. In both penetrating and general-purpose variants, the GBU-31 “has proved effective in surgical and precision strikes against the enemy.”

Monitoring groups, however, have criticized the coalition’s use of such massive bombs in dense urban areas. A July Amnesty International report said coalition and Iraqi forces used explosive weapons unsuitable for Mosul, where militants used civilians as human shields and prevented them from fleeing.

In one case in March, the U.S. dropped a 500-pound bomb GBU-38 bomb, containing the equivalent of 190 pounds of TNT, on a house where two snipers were firing on Iraqi forces. The blast caused secondary explosions, killing more than 100 civilians trapped inside the building — one of the deadliest civilian casualty incidents in recent years.

Amnesty said planners should have known better than use such large ordnance. U.S. officials have re-jected Amnesty’s charges, arguing that planners apply a rigorous process to ensure strikes meet a minimum requirement for proportionality and necessity.

garland.chad@stripes.com Twitter: @chadgarland