US military statistics show that out of every 600 attacks by drones, the percentage of error is only five.

There are 7,000 UAVs currently in use by the armed forces. Some are called Raven, Global Hawk, Shadow, Predator or Reaper. The US Air Force's fleet has grown quickly in recent years to 195 Predators and 28 Reapers in 2009.

The ground crew of a Predator UAV consists of one pilot, a sensor and mission intelligence coordinator. Remote Predator pilots usually have to rely on on-board cameras to see what's going on around the plane. The actual intelligence about the targets usually comes from the commandos on the ground.

The US is the only country operating in Pakistan known to have the ability to launch missiles from drones, carrying out airstrikes on suspected militant targets in tribal areas.

'The US government is spending billions of dollars to expand its fleet of drones and channeling more resources to make more sophisticated UAVs. For instance, till a year ago, the Reaper did not exist and today, the US army has more than two dozen Reaper drones,' Robertson said.

His documentary 'World's Untold Stories: Warfare By Remote' will be telecast on CNN at 2 p.m. and 10 p.m. Saturday as well as 4 a.m. and 8 p.m. Sunday.