When Bush administration officials pointed to Saddam Hussein's unmanned aerial vehicle program and warned how dangerous it was and how it could be used by terrorists, "smart people" pooh-poohed the claim.

Apparently it only took them a few years to realize the threat.

It may sound like science fiction, but the prospect that suicide bombers and hijackers could be made redundant by flying robots is a real one, according to experts.

The technology for remote-controlled light aircraft is now highly advanced, widely available -- and, experts say, virtually unstoppable.

Models with a wingspan of five metres (16 feet), capable of carrying up to 50 kilograms (110 pounds), remain undetectable by radar.

And thanks to satellite positioning systems, they can now be programmed to hit targets some distance away with just a few metres (yards) short of pinpoint accuracy.