In January a small group of U.S. Marines at a remote base near the village of Shurakay in northern Helmand province was running low on ammunition after fighting fiercely for days. The road in was too dangerous for a resupply convoy, and there were so many Taliban fighters that a helicopter crew trying to fly in would have been at serious risk.

Still, the Marines soon heard the soft thwack of rotor blades. They looked up as a glimpse into the future of aviation eased into a hover, then gently descended until a pallet of ammunition dangling beneath it touched the ground. The cargo hook released itself and the unmanned K-MAX helicopter rose again, turned and flew off.

The K-MAX, which is the only drone cargo helicopter in the U.S. military’s fleet, made two more runs to the embattled outpost, dropping off more supplies each time.

It wasn’t a stunt: Over the past 16 months, two K-MAX helicopters that were sent to Afghanistan as an experiment have delivered 3.2 million pounds of cargo across Helmand and flown more than 1,000 missions. That’s reduced the number of supply convoys needed on the province’s bomb-infested roads, eased the workload and risk for helicopter and Osprey crews, saved money and provided real-world proof that drones are practical for much more than surveillance and missile strikes.

The combat-zone test was supposed to last just six months, but in March the Marine Corps extended it indefinitely, citing the K-MAX’s success in delivering cargo and keeping Marines in trucks off dangerous roads.

In the fast-growing world of unmanned aircraft, the K-MAX’s success is a significant step toward what’s expected to be a host of new military and civilian roles for cargo drones, said Peter Singer, the director of the 21st Century Defense Initiative at the Brookings Institution research center and the author of “Wired for War: The Robotics Revolution and Conflict in the 21st Century.”

“Everyone has framed discussion of drones as being about surveillance, and that’s one of the models, but they won’t be only that,” he said.

Indeed, surveillance seems likely to become no more than a niche for drones. Last year, Congress ordered the Federal Aviation Administration to open the airways to the commercial use of drones by 2015. The FAA foresees there will be 10,000 commercial drones flying by 2020. Predicted uses include carrying cargo, lifting construction materials into place, undertaking rescue missions in remote mountains or stormy seas, evacuating the wounded from battlefields and even, some experts half-joke, delivering pizza.

Analysts’ estimates of the commercial market for unmanned aircraft range as high as $94 billion in the next few years.

“The national airspace will be opened, and now that’s not an if, it’s when,” Singer said. “The importance of the K-MAX is that it provides proof of concept that there is a potential commercial use, not just a military one. It’s the best current example of cargo movement by an unmanned aircraft. It’s working a lot, working well and doing so in a pretty tough environment.”

The implications, Singer said, may be extrapolated by looking back at the history of manned aviation. That started with wartime surveillance, then moved onto carrying improvised, then standard, armaments in World War I. After the war, airplanes expanded into moving freight and passengers. The K-MAX and similar competitors are the first shift for drones away from surveillance and air-delivered weapons into freight and the rest of the future for drones, he said.

The Marines also think it’s breaking ground for new drone uses, inside and outside the military.

“It might take some time in the United States for a civilian application, but the crews here are proving it works and that it’s incredibly reliable and cost-effective,” said Maj. Daniel Lindblom, of Alexandria, Va., who oversees the various unmanned-aircraft programs the Marines run in Afghanistan. “It’s just a matter of time.”

The K-MAX looks a little odd, with its side-by-side rotors, narrow fuselage and lack of a tail rotor, but it isn’t startlingly futuristic. That’s because it was based on a manned civilian cargo helicopter that had proved itself for years as Lockheed Martin searched for a simple way to meet the requirements of the test without a vast investment in research and development to build a drone from scratch. It joined forces with the original builder of the K-MAX to convert the helicopter to work by remote operation and automation.

It still has a cockpit, and a pilot can taxi it into place before the cargo is attached or fly it around for maintenance checks. When it’s time to lift the cargo, the pilot flicks a switch to NOLO — “no local operator” — steps out of the cockpit and walks away.

In a converted shipping container nearby, an operator at the helm of a Sony PlayStation video game console takes over, and a crew hooks on the cargo, which dangles on a sling about 75 feet below the K-MAX as it flies off.

The PlayStation is simple, cheap, reliable and already familiar to many people, members of the K-MAX ground crew said. If a controller gums up or breaks, someone drives over to the Marine PX and buys another one, said Phil Melton, a pilot from Priest River, Idaho, who works for Oregon’s Swanson Group Aviation. Swanson has the contract to maintain and operate the K-MAX here.

After takeoff, much of the helicopter’s flight is automated. K-MAX uses GPS satellite navigation to follow a preset path that’s filed with air traffic controllers. There isn’t a video camera aboard, which is one reason it’s important that its routes be carefully coordinated in advance with air traffic controllers and others, such as combat air controllers on the ground. Also that means the ground crew can’t see approaching thunderstorms, so they’re careful to fly only when there’s little chance of a surprise in the weather.

It can travel about 80 miles each way, but it’s best at distances of 58 miles or less because then it can be controlled by a line-of-sight radio system. If it goes farther, the crew has to switch to a less-reliable satellite telephone to control it.

Once it reaches its destination, the ground crew at Camp Bastion is in communication with the troops at the other end, who tell them when the helicopter is in position to ease the cargo down safely. The operator at the PlayStation console hits a “deliver” button and the K-MAX descends automatically at a controlled rate to about 90 feet, then slows the descent to a crawl. When the cargo settles to the ground, a weight sensor triggers the release of the cargo hook, and the K-MAX automatically climbs into the sky again and follows the preset path back to the air base at Camp Bastion, the British side of the massive joint base that includes the main Marine base in Afghanistan, Camp Leatherneck.

All the automation at the delivery end is necessary because the helicopter can dip below the horizon when it descends, meaning the line-of-sight control system no longer works. But it will still automatically set down its cargo and rise back to the point where it’s controllable again.

The program isn’t secret, but it’s almost unknown on base. The helicopters fly from a remote corner of Bastion, mainly at night, when the weather’s usually better and the air cooler and more dense, so the rotor blades are more efficient.

The aircraft now fly six days a week, and up to six flights a day. Often they fly cargoes of water or food, but they also have delivered crucial replacement parts for the improvised bomb-defeating system on a damaged truck and fuel to a small base that was running out.

In Helmand, they’ve built an enviable record of reliability and cost-effectiveness, Lindblom said. The aircraft need only about 1.3 man-hours of maintenance for every hour of flight, and they cost little more than $1,300 an hour to operate, he said. That compares with nearly 23 man-hours for each hour of flight for the CH-53E heavy-lift helicopter and more than $11,000 an hour to operate it, according to statistics supplied by the Marine Corps.

The CH-53E can carry four times as much cargo — the K-MAX is allowed to carry no more than 4,500 pounds per run — and it’s faster, but it also has to fly in pairs for security reasons. That requires a total of 10 crew members and puts them at risk.

The cost savings, performance and reduction in the risk and drudgery mean the wider use of such helicopters, inside and outside the military, is inevitable, Lindblom said.

“This is the wave of the future, and there’s just no question about it,” he said. “About the only problem with it is that we don’t have 20 or 30 more of them.”