STARTING a riot at a football match. Revealing an unknown monument in the desert near Petra. Performing at the Super Bowl. Sneaking drugs and mobile phones into prisons. Herding elephants in Tanzania. What links this astonishing range of activities? They are all things that have been done by small flying robots, better known as drones.

To most people a drone is one of two very different kinds of pilotless aircraft: a toy or a weapon. It is either a small, insect-like device that can sometimes be seen buzzing around in parks or on beaches, or a large military aircraft that deals death from the skies, allowing operators in Nevada to fire missiles at terrorist suspects in Syria. The first category, recreational drones aimed at consumers, are the more numerous by far; around 2m were sold around the world last year. The second category, military drones, account for the vast majority (nearly 90%) of worldwide spending on drones. But after a pivotal year for the civilian drone industry, an interesting space is now opening up in the middle as drones start to be put to a range of commercial uses.

Last year around 110,000 drones (technically known as unmanned aerial vehicles, or UAVs) were sold for commercial use, according to Gartner, a consultancy. That figure is expected to rise to 174,000 this year and the number of consumer drones to 2.8m. Although unit sales of commercial drones are much smaller, total revenues from them are nearly twice as big as for the consumer kind (see chart).