“They’re in the fog, and you’re down hugging the ground trying to fly up the highway and barely able to see it,’’ Ditchey said. “He’s down only 100 feet or so above the ground. In that area of the San Fernando Valley you have mountains on either side of you … and the clouds have obscured them, and you don’t have that much room to maneuver.’’ Los Angeles County Sheriff Alex Villanueva said the precise conditions when the crash occurred are still under investigation, but he acknowledged there was “an issue with visibility and a low ceiling’’ on Sunday.