It’s a bird, it’s a plane, it’s a six-propeller flying vehicle with a nearly eight-foot wingspan. For the next year, delivery drones operated by the British company Skyports are taking daily weekday trips across New York City’s East River, between the tip of Manhattan and a pier in Brooklyn. Since early May—a bit behind schedule—the drones have carried light cargo for a New York City health care system. Right now, those loads are basically a few pounds of paper; once the healthcare system is confident the setup works, it should include nonhazardous, non-biological packages, such as light pharmaceuticals. The drones are part of an experiment run by two New York-New Jersey agencies to discover how a relatively new and sometimes controversial sky-bound delivery tech might fit into a hectic urban environment—and the airspace above it. The pilot program will also try to answer a question that hangs over the entire drone delivery industry: Where does it make sense?…