What is arcing and why does it keep snapping the overhead LRT wires?

Passengers described the mayhem aboard an Air Canada Express flight that crashed into a fire truck at New York’s LaGuardia Airport late Sunday, killing both pilots and leaving dozens injured. Jack Cabot told Fox News the Jazz Aviation flight operated on behalf of Air Canada “came down really hard” around 11:40 p.m. and “stopped really quickly.” About two seconds later, “we just had an absolute, like, slam,” Cabot said. “Everybody was flying everywhere. The plane was sort of veering off left and right,” he said. “It was chaos. It didn’t feel like there was anybody in control.”...