By Paul Cruickshank and Tim Lister
The video recovered by Spanish security services shows a man guiding a large remote-controlled plane in the skies of southern Spain. The plane banks and begins a controlled descent. Two packets drop - one from either wing - to the delight of the "pilot."
According to Fernando Reinares, senior terrorism analyst at Madrid's Elcano Royal Institute, Spanish security services believe the video was made not by an enthusiastic hobbyist, but by a committed terrorist trying to convert a toy plane into a potentially deadly bomber.
The home video was recovered last week, along with explosives, in what Spanish authorities called one of the most significant operations against al Qaeda in the country.
Three men were arrested, including the man seen flying the remote-controlled aircraft. He is Cengiz Yalcin, a Turkish national who lived near Gibraltar, and Spanish authorities allege he was an al Qaeda's cell's facilitator. Two Chechen associates - alleged to have significant expertise in bomb-making - were also arrested.
According to Reinares, Spanish security services suspect the purported cell planned to launch attacks using model aircraft to coincide with the London Olympics, and that one of their targets was a shopping center near Gibraltar.
The notion that terrorists could use their own crude versions of pilotless drones might seem fantastical - a scenario dreamed up and posted on blogs by radio-controlled aircraft hobbyists in their darker moments. But this is not the first time that model planes have featured in a terrorist investigation.
Last month Rezwan Ferdaus, a Massachusetts resident inspired by al Qaeda's ideology, pleaded guilty to a plot to fly a remote-controlled plane with high explosives into the Pentagon and U.S. Capitol. He had been arrested in September 2011. According to court documents, Rezwan, a Northeastern University graduate with a degree in physics, planned to use a model of the F-86 Sabre, a fighter jet in the Korean War, packed with C4 explosives.
Miniature versions of the plane - between 5 feet and 6 feet, 6 inches long - can be acquired for less than $200 from websites serving model plane enthusiasts. "Provides authoritative rudder control so you can execute point rolls and knife-edge flight with precision," reads the promotion material for the model on one website.
According to court documents, one of these F-86 models was delivered in August 2011 to a storage facility in Framingham, Massachusetts, that Ferdaus had rented under a false name to build his attack planes and maintain his equipment. He was arrested the following month in an FBI sting operation, after undercover agents handed him the explosives.
Authorities said Ferdaus had planed to fill three remote-controlled aircraft - which he referred to as "small drone airplanes" - with explosives, launch them from an east Potomac park, and guide them by GPS into their targets.
And before Ferdaus, Christopher Paul, a Columbus, Ohio, resident pleaded guilty in 2008 to planning terrorist attacks in the United States and Europe. According to the indictment in that case, Paul conducted research in 2006 on a variety of remote-controlled models, including a boat and a 5-foot-long helicopter. Paul was accused of joining al Qaeda in the early 1990s.
According to a U.S. Government Accountability Office report published last month, Ferdaus' plot "highlighted the potential for model aircraft to be used for non-approved or unintended purposes." But the report stated that "apart from FAA's voluntary safety standards for model aircraft operators, FAA (the Fedeal Aviation Administration) has no regulations relating to model aircraft." According to the report, new rules set to be introduced in late 2012 may require certain model aircraft to be registered.
Advances in remote-control technology mean that there are now a wide variety of easily purchased machines that terrorists might contemplate using. And dozens of videos uploaded to social media sites show models as long as 12 feet and as sophisticated as the C-17 - some capable of flying at speeds of more than 100 mph.
One remote-controlled helicopter that retails online for $10,000 in the U.S. is described as capable of lifting a payload of at least 20 pounds (9 kilograms) It can be accessorized with a built-in camera providing real-time video transmitted back to the controller, a feature that would be of obvious help to terrorists seeking to home in on a target - and record a propaganda video of the attack at the same time.
In some ways, the idea echoes - albeit in primitive fashion - the growing use by the United States and other governments of unmanned drones for surveillance and missile strikes against terrorist targets. The use of drones has had a dramatic impact in the campaign against al Qaeda and other terror groups in Pakistan - and is now being expanded to the Horn of Africa and Yemen.
Hezbollah, the Shiite militia in Lebanon, reportedly carried out an armed drone attack on an Israeli naval vessel during the 2006 Lebanon war. The Haaretz newspaper reported at the time that the ship was attacked by an explosives-laden drone, which would have been undetected by radar. Four Israeli sailors were killed. And a raid on a camp of the FARC terrorist group in Colombia in 2002 uncovered nine remote-controlled planes, one of which had already been packed with plastic explosive.
In 2006, a Maryland teacher, Ali Asad Chandia, was convicted of trying to acquire an electronic automatic pilot system for a model aircraft on behalf of the Pakistani terror group Lashkar e Tayiba. The system contains a stability and control computer that can be programmed to fly a plane with a 10- to 12-foot wingspan using GPS co-ordinates and can be programmed to turn a video camera on and off when the plane reaches certain locations.
As long ago as 2004, the Department of Homeland Security sent out an information bulletin asking trainers and hobby shop owners to report suspicious purchases. Another bulletin in 2008 said the DHS and FBI "assess that terrorists could use explosives-laden RCMA (radio-controlled model aircraft) singly or in groups to circumvent ground-based defenses at targeted infrastructure." And a study by the Institute for Defense Analyses a few years back concluded: "There would be little danger of detection in transportation, launch, or escape assuming that everything was planned in advance."
Such advances, combined with precise mapping services like Google Earth, may also provide terrorist operatives with opportunities to strike targets several miles away. However, most standard model aircraft can only stay aloft for about 30 minutes and the operator must maintain a constant line of sight.
And detonating C4, a very stable explosive insensitive to most physical shocks, on a model plane would be a challenge. Even 20 pounds of high explosive would be unlikely to inflict devastating structural damage on a building - especially if it were reinforced like the Pentagon.
That said, the explosive impact of a few pounds of C4 in a confined and crowded space such as a sports stadium or concert venue could produce mass casualties. Some studies have suggested that spraying chemical payloads, while not as lethal, could have a greater psychological effect. Unmanned helicopters for crop-spraying - though often costing six figures - are commercially available and can carry a payload of up to 40 pounds.
And technology - miniaturization, GPS guidance, wireless video - will enhance the capabilities of model planes.
"Terrorists innovate and adapt to security measures, we have to always keep this in mind," Reinares told CNN.