The recent spate of unidentified drone sightings in the U.S., including some near sensitive locations such as airports and military installations, has caused significant public concern. Some of this recent increase in activity may be related to a September 2023 change in U.S. Federal Aviation Administration regulations that now allow drone operators to fly at night. But most of the sightings are likely airplanes or helicopters rather than drones. The inability of the U.S. government to definitively identify the aircraft in the recent incidents, however, has some people wondering, why can’t they? I am an engineer who studies defense systems.…