Planes without pilots

Just how big are these drones?
They range in size from surveillance craft small enough to fit into your hand to Northrop Grumman's Global Hawk that has the wing-span of a Boeing 737 and is expected to replace America's U-2 spy plane. The best-known US military drone – or UAV (Unmanned Aerial Vehicle) – is the Predator, a 27-foot-long aircraft made of lightweight graphite and carbon fibre, which is used extensively in Iraq and Afghanistan, and increasingly in Pakistan. "The key thing in a UAV," says Damian Kemp, an editor at Jane's Defence Weekly, "is that it does missions that are dull, dirty and dangerous."

Have drones proved to be effective?
Enormously so. In the past six months alone, Predators operating in the tribal regions of Pakistan and Afghanistan are credited with helping capture or kill nearly half the terrorists on a list of 20 "high-value targets": some military analysts believe that al-Qa'eda has been crippled as a result. US forces claim to have killed Khalid Habib, al-Qaeda's third-ranking member, Abu Khabab al-Masri, its chemical and biological weapons chief, and Osama bin Laden's son, Saad. Thanks to drones "a significant fraction of the al-Qa'eda leadership in that part of the world has been taken off the battlefield", says CIA director Michael Hayden. There are now 5,000 drones in the US military: in 2010, the US air force will, for the first time, order more drones than manned aircraft.

And how do drones operate?
Predators, each carrying two laser-guided Hellfire missiles, can stay aloft for up to 40 hours at a time and, having no pilot, require no rest. Flying at altitudes up to 25,000 feet, their quiet engines are very hard to detect from the ground. Using infrared sensors, radar and zoom cameras so powerful that they can distinguish a person's facial features from five miles up, a Predator can capture still and video images day or night, in any weather, and transmit them in real time to pilots thousands of miles away.

And where do the Predator pilots sit?
Mission control is at Creech air force base outside Las Vegas. The armchair pilots operate up to four drones at once, enabling them to fly missions in Iraq and Afghanistan on the same day. Using video screens and computer consoles, 250 pilots work round the clock, guiding drones 7,000 miles away and scanning the ground for suspicious activity. When a target is identified, commanders on the ground in Iraq or Afghanistan decide whether to attack. "When you're on the radio with a guy on the ground, and he is out of breath and you can hear the weapons fire in the background, you are every bit as engaged as if you were actually there," Major Matthew Morrison, a drone pilot, told the New York Times.Does only the US use drones?
Far from it. Remote-controlled aircraft have existed since the First World War, and dozens of countries have drones of one sort or another. Israel, a leader in drone technology, has used them since the Seventies for surveillance and missile attacks in the Palestinian territories. The 32nd Regiment of the Royal Artillery, the UK's specialised drone unit, has flown UAVs extensively since the 1999 Kosovo war. The UK uses Israeli-built Hermes drones in Afghanistan, but 54 Watchkeeper drones, an unarmed joint French, British and Israeli model, should come into service next year. And drones are increasingly used for civilian purposes, too.

Do drones have major drawbacks?
Yes. US air force officials admit that more than a third of their unmanned Predator spy planes have crashed, mostly in Iraq and Afghanistan. One reason for that, say the pilots who control them from afar, is that some of the controls are clunky, and the missile-firing button sits dangerously close to the switch that shuts off the plane's engines. Another problem is that good drone pilots are in such short supply that the air force recently put out a call for retirees to help. But their biggest drawback is that they often kill the wrong people.

Who are the casualties?
Last year, Predator missiles hit a wedding party in Afghanistan, killing 30 civilians, including children. Dozens of Predator strikes in the Waziristan borderlands of Afghanistan and Pakistan since last August have killed or nearly killed those in the vicinity of the strike. No surprise then, that these attacks cause huge resentment among the local population. David Kilcullen, who helped design the Iraq surge strategy, believes that Predators are making as many enemies as those they have killed off. "We need to call off the drones," he recently told the US Congress.

What happens during a strike?
Silence... followed by a powerful explosion. "It's not like any other plane," an unnamed militant in Gaza told the Associated Press. "You don't see the missile leaving. It's very quiet." The prospect of drones hovering overhead has so unnerved al-Qaeda and Taliban leaders in Afghanistan and Pakistan, according to a recent intelligence report, that some sleep under trees at night rather than risk an attack on their homes. Sara Carter, a reporter for the Washington Times, described a video of a drone attack on a group of men outside a large building as follows: "In an instant, the men on the ground and the building disappeared in an explosion of brilliant white light."

What is the future of drones?
Engineers are working to make drones self-sufficient, so they can repair themselves if disabled. More are also now able to land themselves – reducing the number of crash landings – and the machines are becoming ever more deadly. There are now 28 Reapers, the successor to the Predator, in the US air force. Reapers fly at 50,000 feet, carry not two but 14 Hellfire missiles, and can distinguish the "heat signatures" of rocket launchers, anti-aircraft guns and other weapons on the ground. The US government envisions a future in which drones will remain aloft for months, if not years, at a time, using fuel cells or constantly refuelling while airborne. "These systems today are very much Model T Fords," says defence analyst PW Singer. "These things will only get more advanced." ·