Information of TTFLY: President Barack Obama has confirmed the US is using unmanned aircraft to target suspected militants in tribal areas of Pakistan. He defended the drone attacks, saying they made precision strikes and were kept on a "tight leash". What are drones used for and how are they controlled?

To the military, they are UAVs (Unmanned Aerial Vehicles) or RPAS (Remotely Piloted Aerial Systems). However, they are more commonly known as drones.

Drones are used in situations wher manned flight is considered too risky or difficult. They provide troops with a 24-hour "eye in the sky", seven days a week. Each aircraft can stay aloft for up to 17 hours at a time, loitering over an area and sending back real-time imagery of activities on the ground.

Those used by the United States Air Force and Royal Air Force range from small intelligence, surveillance and reconnaissance craft, some light enough to be launched by hand, to medium-sized armed drones and large spy planes.

Although the US does not routinely speak publicly about operations involving drones, President Obama has confirmed that they regularly strike suspected militants in Pakistan's tribal areas.

The use of such unmanned aircraft in the area began under President George W Bush, but their use has more than doubled under the Obama administration.

Drones are seen by many in the military as delivering precision strikes without the need for more intrusive military action. However, they are not without controversy.

Hundreds of people have been killed by the strikes in Pakistan - civilians as well as militants, causing outrage. One of the deadliest attacks was in March 2011 when 40 were killed, many believed to be civilians at a tribal meeting.