Aerial firefighting is already one of the most dangerous kinds of aviation there is. Pilots must maneuver heavy, sluggish planes over rough terrain at low altitude, often amid severe turbulence and poor visibility. Now aerial firefighters battling the Los Angeles wildfires are facing an additional danger: illegal drones. On Thursday a “Super Scooper” plane fighting the Palisade fire collided with a drone that tore a hole in its wing...