Operators will have to register devices over a certain size and take a test to assure proper use The U.K. will require operators of many hobby drones to register them with the government and take a test to assure proper use amid growing global concern the increasingly popular unmanned planes pose a threat to aviation. The U.S. Federal Aviation Administration and European authorities have registered an increasing number of incidents in which drones have come worryingly close to airliners. In several cases airports have had to temporarily halt operations after drones were detected that could have endangered flights. The British government said it was taking action after research showed drones weighing as little as 400 grams (0.9 pound) could damage the windscreens of helicopters. It would take…