FARNBOROUGH: Having revolutionised warfare for the United States in the last 15 years, unmanned aerial drones are going global as the number of countries building and operating them soars.

Until now, such systems have largely been the exclusive purview of the US and a handful of allies. Washington allowed Britain, Italy and Turkey to buy US-built drones and operate them usually alongside US forces, but largely rejected requests from other nations keen to acquire the same capability.

But that is quickly changing. US firm General Atomics expects to make its first sales of an unarmed version of its Predator drones this year, with Latin America and the Middle East seen to be particularly fertile markets.

"There has been very considerable international interest," retired US Navy Rear Admiral Christopher Ames, now director of international strategic development for the company, told Reuters at this week's Farnborough International Airshow.

Flanked by video screens showing the firm's products in action in Iraq, Afghanistan and tracking pirates over the Indian Ocean, Ames said their combat record spoke for itself.

Not only were human air crew not put at risk, he said, but use of unmanned aerial vehicles (UAVs) also offered huge savings in fuel and personnel costs over conventional manned aircraft.

"The nations that have been operating with us in coalition... have seen what it can do in practice," he said.. "Their conviction goes beyond what marketing hype can provide."

Privately owned San Diego-based General Atomics was one of the pioneers of early drone technology, operating them first in the Balkans in the 1990s. While the Israeli military has long embraced unmanned aircraft, recruiting specialists directly from model aircraft clubs, other air forces including that of the United States were initially distinctly skeptical.

But the wars that followed the attacks of Sept. 11, 2001 changed all that. In Iraq, Afghanistan, Pakistan, Yemen, Somalia and elsewhere, US forces have become increasingly reliant on drones ranging from tiny aircraft operated by infantrymen to those that can fly hundreds or even thousands of miles and stay aloft over 24 hours.

Under the presidency of Barack Obama in particular, they have often been the weapon of choice for targeted killings of leading al Qaeda militants, as well as a favourite tool for long-range spy flights over potentially unfriendly countries.

The winding down of combat operations in Afghanistan may reduce the current level of US drone demand, industry executives say. But the global market, they suspect, is only beginning to hot up.

Until now, Washington has remained able to exercise considerable control over even those drones it has sold abroad. Britain's Royal Air Force, for example, bases the pilots flying its drones over Afghanistan at a US air force base in Nevada alongside their US counterparts.

That, experts say, cannot last.

Drones Pride of Place

"In the future, if you're a moderately serious air force... you're going to want to have at least a medium-level endurance drone with the capability to mount reconnaissance and probably deploy weapons," says Douglas Barrie, a senior fellow for aerospace at London's International Institute for Strategic Studies. "It also may or may not be stealthy... We are only at the very beginning of that now."

With aircraft such as Predator, the much longer-range Global Hawk built by Northrop Grumman Corp and the top-secret and stealthy Lockheed Martin Sentinel - one of which crashed and was captured on an apparent mission over Iran last year - the United States remains by far the leader of the pack.

But perhaps inevitably, the gap is closing.

At this year's Farnborough Air Show, almost every major international aircraft maker brought with them their own latest drone. Outside its large chalet, Britain's BAE Systems displayed its long-range Taranis stealth UAV prototype in prime position alongside its Hawk trainer - the aircraft used by the RAF's Red Arrows display team - as well as a World War Two-era Spitfire.

"What we're looking at is effectively jumping straight to the next generation," said Martin Rowe-Wilcocks, BAE head of international business development for future combat air systems. "We're able to look at those systems that are already in service and learn from them."

Israel has long sold small unarmed drones to a range of countries, but other producers are also muscling in. Russian news agency RIA Novosti reported in April that Russia hoped to fly its first prototype domestically produced armed drone as soon as 2014.

China has made it clear it is interested in building similar systems, and both countries are expected to have done what they can to persuade Tehran to share its captured Sentinel.

As demand but also international competition rises, some US firms worry Washington's attempts to slow the spread of drone technology may leave it falling behind.

Diplomatic cables released by WikiLeaks show several countries including United Arab Emirates and Saudi Arabia asking US officials to buy armed drones but being rebuffed.

Washington says its commitments to the Missile Technology Control Regime (MTCR), a non-binding international agreement designed to limit the spread of long-range precision weaponry, restrict drone export.

US Firms Disadvantaged

Industry leaders warn that could see the US drone sector going the way of its commercial satellite production, effectively strangled by export controls seen as effectively killing its dominance of the sector just as new rivals emerge.

"The unmanned area is growing by leaps and bounds," says Marion Blakey, president of the Aerospace Industries Association. "The Missile Technology Control Regime is something that really needs to be addressed because it's disadvantaging US industry."

The export-variant Predator, General Atomics says, should deal with some of those concerns. It will have no "hard points" to attach missiles and would be deliberately engineered to make adding new weaponry impossible, it says.

Retailing at $3-4 million an item, the unarmed export drone is way cheaper than most equivalent aircraft, Ames said.

"There are countries that for a long time have been asking for Predator," he said. "It (the export variant) opens that up to us."

Other US defence firms are also investing growing quantities of their own money in new and innovative UAVs. Boeing recently test-flew its prototype "Phantom Eye", a high-altitude drone capable of staying airborne for days at a time.

Even if foreign markets remain sometimes off-limits, the Pentagon is seen as still keen to expand the use of drones into new areas. Lockheed Martin says it is investing in unmanned technologies and plans to compete for a future US Navy contract to build a next-generation drone that will operate from aircraft carriers.

That contest is also likely to include Northrop Grumman Corp, maker of the X-47B, a US Navy program that is demonstrating some of the initial capabilities that would be packed on the future carrier drones.

Officials say Britain is also increasingly interested in naval drones to operate from carriers as well as a range of smaller warships. But BAE's Rowe-Wilcocks says the real growth area will ultimately be the civilian sector.

Within a decade or so, he believes unmanned aircraft will routinely operate in European air space, providing surveillance for law enforcement agencies, maritime patrol and a host of other functions.

"The test will be whether the public will accept unmanned aircraft overhead in the way they accept those with someone in the cockpit," he says. "At this stage, I think we're more or less there technologically. It is really going to be a regulatory and particularly cultural challenge."