Estimates suggest that people in the United States now own over one million unmanned aircraft systems (UAS), commonly known as drones, with the number growing each year. Recreational and other unregulated use of drones presents safety risks to manned aircraft, their crews, airline passengers, and anyone below their flight paths. Unauthorized UAS flights recently interfered with aerial tankers battling wildfires, which grounded the tankers and put firefighters on the ground at greater risk [USDOT FAA 2015a]. In April 2016 a pilot for a British Airways plane stated that a drone may have struck the plane as it landed at London’s Heathrow airport. While the plane landed undamaged, and a subsequent investigation was halted due to lack of evidence, the prospect of a drone damaging a commercial flight attracted worldwide concern [theguardian.com].

In 2014 pilots reported 238 unmanned aircraft sightings in the United States alone. There were about 5 times as many sightings (about 1,210) in 2015 from pilots of all aircraft types, including large, commercial passenger aircraft. In June 2015, during the height of the summer season for hobbyists, 138 pilots reported seeing drones at altitudes up to 10,000 feet, a sizable increase from 16 reported sightings in June 2014. Many other drones were reported in unauthorized places, such as near airports [USDOT FAA 2016b].

Prior to operating unmanned aircraft, the Federal Aviation Administration (FAA) requires people to file a paper registration application for drones weighing 55 pounds or more.  In December 2015, FAA also issued an interim final rule for online registration of drones weighing from 0.55 pounds up to just under 55 pounds, as an alternative to filing a paper application. Very light drones that weigh less than 0.55 pounds do not have to be registered [USDOT FAA 2015c]. The FAA announced in March 2016 that nearly 400,000 small drones under 55 pounds were registered.