A solar-powered surveillance drone with a wingspan larger than a Boeing 747 jumbo jet could fly for weeks or months at a time, according to its operator, while watching for drug-smuggling vessels, pirates or naval warships. It has been performing test flights off the US Gulf Coast this month. The Skydweller drone, operated by US-Spanish firm Skydweller Aero, has a wingspan of 72 metres – exceeding the width of most commercial passenger jets. But it weighs only about 2500 kilograms – as much as a Ford F-150 truck. It is based on the Solar Impulse 2 aircraft, which performed the first solar-powered flight around the world in 2016. Skydweller Aero purchased and converted the pioneering aircraft with the goal of building a fleet of similar solar-powered, carbon-fibre drones capable of "perpetual flight" at altitudes exceeding 13 kilometres in daytime hours.